How to delete or add column in SQLITE? - sqlite

I want to delete or add column in sqlite database
I am using following query to delete column.
ALTER TABLE TABLENAME DROP COLUMN COLUMNNAME
But it gives error
System.Data.SQLite.SQLiteException: SQLite error
near "DROP": syntax error

ALTER TABLE SQLite
SQLite supports a limited subset of ALTER TABLE. The ALTER TABLE command in SQLite allows the user to rename a table or to add a new column to an existing table. It is not possible to rename a column, remove a column, or add or remove constraints from a table.
You can:
create new table as the one you are trying to change,
copy all data,
drop old table,
rename the new one.

SQLite 3.35.0 introduced support for ALTER TABLE DROP COLUMN.
ALTER TABLE
The DROP COLUMN syntax is used to remove an existing column from a table. The DROP COLUMN command removes the named column from the table, and also rewrites the entire table to purge the data associated with that column. The DROP COLUMN command only works if the column is not referenced by any other parts of the schema and is not a PRIMARY KEY and does not have a UNIQUE constraint.
The following syntax will be valid:
ALTER TABLE <TABLENAME> DROP COLUMN <COLUMNNAME>;
ALTER TABLE <TABLENAME> DROP <COLUMNNAME>;

I've wrote a Java implementation based on the Sqlite's recommended way to do this:
private void dropColumn(SQLiteDatabase db,
ConnectionSource connectionSource,
String createTableCmd,
String tableName,
String[] colsToRemove) throws java.sql.SQLException {
List<String> updatedTableColumns = getTableColumns(tableName);
// Remove the columns we don't want anymore from the table's list of columns
updatedTableColumns.removeAll(Arrays.asList(colsToRemove));
String columnsSeperated = TextUtils.join(",", updatedTableColumns);
db.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;");
// Creating the table on its new format (no redundant columns)
db.execSQL(createTableCmd);
// Populating the table with the data
db.execSQL("INSERT INTO " + tableName + "(" + columnsSeperated + ") SELECT "
+ columnsSeperated + " FROM " + tableName + "_old;");
db.execSQL("DROP TABLE " + tableName + "_old;");
}
To get the table's column, I used the "PRAGMA table_info":
public List<String> getTableColumns(String tableName) {
ArrayList<String> columns = new ArrayList<String>();
String cmd = "pragma table_info(" + tableName + ");";
Cursor cur = getDB().rawQuery(cmd, null);
while (cur.moveToNext()) {
columns.add(cur.getString(cur.getColumnIndex("name")));
}
cur.close();
return columns;
}
I actually wrote about it on my blog, you can see more explanations there:
http://udinic.wordpress.com/2012/05/09/sqlite-drop-column-support/

As others have pointed out
It is not possible to rename a column, remove a column, or add or
remove constraints from a table.
source : http://www.sqlite.org/lang_altertable.html
While you can always create a new table and then drop the older one.
I will try to explain this workaround with an example.
sqlite> .schema
CREATE TABLE person(
id INTEGER PRIMARY KEY,
first_name TEXT,
last_name TEXT,
age INTEGER,
height INTEGER
);
sqlite> select * from person ;
id first_name last_name age height
---------- ---------- ---------- ---------- ----------
0 john doe 20 170
1 foo bar 25 171
Now you want to remove the column height from this table.
Create another table called new_person
sqlite> CREATE TABLE new_person(
...> id INTEGER PRIMARY KEY,
...> first_name TEXT,
...> last_name TEXT,
...> age INTEGER
...> ) ;
sqlite>
Now copy the data from the old table
sqlite> INSERT INTO new_person
...> SELECT id, first_name, last_name, age FROM person ;
sqlite> select * from new_person ;
id first_name last_name age
---------- ---------- ---------- ----------
0 john doe 20
1 foo bar 25
sqlite>
Now Drop the person table and rename new_person to person
sqlite> DROP TABLE IF EXISTS person ;
sqlite> ALTER TABLE new_person RENAME TO person ;
sqlite>
So now if you do a .schema, you will see
sqlite>.schema
CREATE TABLE "person"(
id INTEGER PRIMARY KEY,
first_name TEXT,
last_name TEXT,
age INTEGER
);

DB Browser for SQLite allows you to add or drop columns.
In the main view, tab Database Structure, click on the table name. A button Modify Table gets enabled, which opens a new window where you can select the column/field and remove it.

At one time this was not directly supported and you would need to follow a four-step process: (1) create a temporary_table, (2) copy the data, (3) drop the old table, and then (4) rename the temporary_table.
But now that these features are supported, all you need to do is upgrade SQLite.
3.35.0 from 2021-03-12 adds ALTER TABLE DROP COLUMN
3.25.0 from 2018-09-15 added ALTER TABLE RENAME COLUMN
3.2.0 from way back in 2005-03-21 added ALTER TABLE ADD COLUMN
Note that there are still some edge cases where these may not work, e.g., you cannot drop a primary key column. See the documentation for more details. When these ALTER TABLE … COLUMN statements do not work, you can fall back to the four-step process.
By the way the four-step process is really a twelve-step process in the docs. But four of those steps are really important, easy to get wrong, and specifically called out in those docs.

http://www.sqlite.org/lang_altertable.html
As you can see in the diagram, only ADD COLUMN is supported. There is a (kinda heavy) workaround, though: http://www.sqlite.org/faq.html#q11

We cannot drop a specific column in SQLite 3. See the FAQ.

As others have pointed out, sqlite's ALTER TABLE statement does not support DROP COLUMN, and the standard recipe to do this does not preserve constraints & indices.
Here's some python code to do this generically, while maintaining all the key constraints and indices.
Please back-up your database before using! This function relies on doctoring the original CREATE TABLE statement and is potentially a bit unsafe - for instance it will do the wrong thing if an identifier contains an embedded comma or parenthesis.
If anyone would care to contribute a better way to parse the SQL, that would be great!
UPDATE I found a better way to parse using the open-source sqlparse package. If there is any interest I will post it here, just leave a comment asking for it ...
import re
import random
def DROP_COLUMN(db, table, column):
columns = [ c[1] for c in db.execute("PRAGMA table_info(%s)" % table) ]
columns = [ c for c in columns if c != column ]
sql = db.execute("SELECT sql from sqlite_master where name = '%s'"
% table).fetchone()[0]
sql = format(sql)
lines = sql.splitlines()
findcol = r'\b%s\b' % column
keeplines = [ line for line in lines if not re.search(findcol, line) ]
create = '\n'.join(keeplines)
create = re.sub(r',(\s*\))', r'\1', create)
temp = 'tmp%d' % random.randint(1e8, 1e9)
db.execute("ALTER TABLE %(old)s RENAME TO %(new)s" % {
'old': table, 'new': temp })
db.execute(create)
db.execute("""
INSERT INTO %(new)s ( %(columns)s )
SELECT %(columns)s FROM %(old)s
""" % {
'old': temp,
'new': table,
'columns': ', '.join(columns)
})
db.execute("DROP TABLE %s" % temp)
def format(sql):
sql = sql.replace(",", ",\n")
sql = sql.replace("(", "(\n")
sql = sql.replace(")", "\n)")
return sql

I rewrote the #Udinic answer so that the code generates table creation query automatically. It also doesn't need ConnectionSource. It also has to do this inside a transaction.
public static String getOneTableDbSchema(SQLiteDatabase db, String tableName) {
Cursor c = db.rawQuery(
"SELECT * FROM `sqlite_master` WHERE `type` = 'table' AND `name` = '" + tableName + "'", null);
String result = null;
if (c.moveToFirst()) {
result = c.getString(c.getColumnIndex("sql"));
}
c.close();
return result;
}
public List<String> getTableColumns(SQLiteDatabase db, String tableName) {
ArrayList<String> columns = new ArrayList<>();
String cmd = "pragma table_info(" + tableName + ");";
Cursor cur = db.rawQuery(cmd, null);
while (cur.moveToNext()) {
columns.add(cur.getString(cur.getColumnIndex("name")));
}
cur.close();
return columns;
}
private void dropColumn(SQLiteDatabase db, String tableName, String[] columnsToRemove) {
db.beginTransaction();
try {
List<String> columnNamesWithoutRemovedOnes = getTableColumns(db, tableName);
// Remove the columns we don't want anymore from the table's list of columns
columnNamesWithoutRemovedOnes.removeAll(Arrays.asList(columnsToRemove));
String newColumnNamesSeparated = TextUtils.join(" , ", columnNamesWithoutRemovedOnes);
String sql = getOneTableDbSchema(db, tableName);
// Extract the SQL query that contains only columns
String oldColumnsSql = sql.substring(sql.indexOf("(")+1, sql.lastIndexOf(")"));
db.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;");
db.execSQL("CREATE TABLE `" + tableName + "` (" + getSqlWithoutRemovedColumns(oldColumnsSql, columnsToRemove)+ ");");
db.execSQL("INSERT INTO " + tableName + "(" + newColumnNamesSeparated + ") SELECT " + newColumnNamesSeparated + " FROM " + tableName + "_old;");
db.execSQL("DROP TABLE " + tableName + "_old;");
db.setTransactionSuccessful();
} catch {
//Error in between database transaction
} finally {
db.endTransaction();
}
}

I have improved user2638929 answer and now it can preserves column type, primary key, default value etc.
public static void dropColumns(SQLiteDatabase database, String tableName, Collection<String> columnsToRemove){
List<String> columnNames = new ArrayList<>();
List<String> columnNamesWithType = new ArrayList<>();
List<String> primaryKeys = new ArrayList<>();
String query = "pragma table_info(" + tableName + ");";
Cursor cursor = database.rawQuery(query,null);
while (cursor.moveToNext()){
String columnName = cursor.getString(cursor.getColumnIndex("name"));
if (columnsToRemove.contains(columnName)){
continue;
}
String columnType = cursor.getString(cursor.getColumnIndex("type"));
boolean isNotNull = cursor.getInt(cursor.getColumnIndex("notnull")) == 1;
boolean isPk = cursor.getInt(cursor.getColumnIndex("pk")) == 1;
columnNames.add(columnName);
String tmp = "`" + columnName + "` " + columnType + " ";
if (isNotNull){
tmp += " NOT NULL ";
}
int defaultValueType = cursor.getType(cursor.getColumnIndex("dflt_value"));
if (defaultValueType == Cursor.FIELD_TYPE_STRING){
tmp += " DEFAULT " + "\"" + cursor.getString(cursor.getColumnIndex("dflt_value")) + "\" ";
}else if(defaultValueType == Cursor.FIELD_TYPE_INTEGER){
tmp += " DEFAULT " + cursor.getInt(cursor.getColumnIndex("dflt_value")) + " ";
}else if (defaultValueType == Cursor.FIELD_TYPE_FLOAT){
tmp += " DEFAULT " + cursor.getFloat(cursor.getColumnIndex("dflt_value")) + " ";
}
columnNamesWithType.add(tmp);
if (isPk){
primaryKeys.add("`" + columnName + "`");
}
}
cursor.close();
String columnNamesSeparated = TextUtils.join(", ", columnNames);
if (primaryKeys.size() > 0){
columnNamesWithType.add("PRIMARY KEY("+ TextUtils.join(", ", primaryKeys) +")");
}
String columnNamesWithTypeSeparated = TextUtils.join(", ", columnNamesWithType);
database.beginTransaction();
try {
database.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;");
database.execSQL("CREATE TABLE " + tableName + " (" + columnNamesWithTypeSeparated + ");");
database.execSQL("INSERT INTO " + tableName + " (" + columnNamesSeparated + ") SELECT "
+ columnNamesSeparated + " FROM " + tableName + "_old;");
database.execSQL("DROP TABLE " + tableName + "_old;");
database.setTransactionSuccessful();
}finally {
database.endTransaction();
}
}
PS. I used here android.arch.persistence.db.SupportSQLiteDatabase, but you can easyly modify it for use android.database.sqlite.SQLiteDatabase

I guess what you are wanting to do is database migration. 'Drop'ping a column does not exist in SQLite. But you can however, add an extra column by using the ALTER table query.

you can use Sqlitebrowser. In the browser mode, for the respective database and the table, under the tab -database structure,following the option Modify Table, respective column could be removed.

You can use the SQlite Administrator for changing the column names.
Right Click on Table name and select Edit Table.Here you will find the table structure and you can easily rename it.

As SQLite has limited support to ALTER TABLE so you can only ADD column at end of the table OR CHANGE TABLE_NAME in SQLite.
Here is the Best Answer of HOW TO DELETE COLUMN FROM SQLITE?
visit Delete column from SQLite table

As an alternative:
If you have a table with schema
CREATE TABLE person(
id INTEGER PRIMARY KEY,
first_name TEXT,
last_name TEXT,
age INTEGER,
height INTEGER
);
you can use a CREATE TABLE...AS statement like CREATE TABLE person2 AS SELECT id, first_name, last_name, age FROM person;, i.e. leave out the columns you don't want. Then drop the original person table and rename the new one.
Note this method produces a table has no PRIMARY KEY and no constraints. To preserve those, utilize the methods others described to create a new table, or use a temporary table as an intermediate.

This answer to a different question is oriented toward modifying a column, but I believe a portion of the answer could also yield a useful approach if you have lots of columns and don't want to retype most of them by hand for your INSERT statement:
https://stackoverflow.com/a/10385666
You could dump your database as described in the link above, then grab the "create table" statement and an "insert" template from that dump, then follow the instructions in the SQLite FAQ entry "How do I add or delete columns from an existing table in SQLite." (FAQ is linked elsewhere on this page.)

Implementation in Python based on information at http://www.sqlite.org/faq.html#q11.
import sqlite3 as db
import random
import string
QUERY_TEMPLATE_GET_COLUMNS = "PRAGMA table_info(#table_name)"
QUERY_TEMPLATE_DROP_COLUMN = """
BEGIN TRANSACTION;
CREATE TEMPORARY TABLE #tmp_table(#columns_to_keep);
INSERT INTO #tmp_table SELECT #columns_to_keep FROM #table_name;
DROP TABLE #table_name;
CREATE TABLE #table_name(#columns_to_keep);
INSERT INTO #table_name SELECT #columns_to_keep FROM #tmp_table;
DROP TABLE #tmp_table;
COMMIT;
"""
def drop_column(db_file, table_name, column_name):
con = db.connect(db_file)
QUERY_GET_COLUMNS = QUERY_TEMPLATE_GET_COLUMNS.replace("#table_name", table_name)
query_res = con.execute(QUERY_GET_COLUMNS).fetchall()
columns_list_to_keep = [i[1] for i in query_res if i[1] != column_name]
columns_to_keep = ",".join(columns_list_to_keep)
tmp_table = "tmp_%s" % "".join(random.sample(string.ascii_lowercase, 10))
QUERY_DROP_COLUMN = QUERY_TEMPLATE_DROP_COLUMN.replace("#table_name", table_name)\
.replace("#tmp_table", tmp_table).replace("#columns_to_keep", columns_to_keep)
con.executescript(QUERY_DROP_COLUMN)
con.close()
drop_column(DB_FILE, TABLE_NAME, COLUMN_NAME)
This script first makes random temporary table and inserts data of only necessary columns except the one that will will be dropped. Then restores the original table based on the temporary table and drops the temporary table.

My solution, only need to call this method.
public static void dropColumn(SQLiteDatabase db, String tableName, String[] columnsToRemove) throws java.sql.SQLException {
List<String> updatedTableColumns = getTableColumns(db, tableName);
updatedTableColumns.removeAll(Arrays.asList(columnsToRemove));
String columnsSeperated = TextUtils.join(",", updatedTableColumns);
db.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tableName + "_old;");
db.execSQL("CREATE TABLE " + tableName + " (" + columnsSeperated + ");");
db.execSQL("INSERT INTO " + tableName + "(" + columnsSeperated + ") SELECT "
+ columnsSeperated + " FROM " + tableName + "_old;");
db.execSQL("DROP TABLE " + tableName + "_old;");
}
And auxiliary method to get the columns:
public static List<String> getTableColumns(SQLiteDatabase db, String tableName) {
ArrayList<String> columns = new ArrayList<>();
String cmd = "pragma table_info(" + tableName + ");";
Cursor cur = db.rawQuery(cmd, null);
while (cur.moveToNext()) {
columns.add(cur.getString(cur.getColumnIndex("name")));
}
cur.close();
return columns;
}

At least as of version 3.37.0, sqlite3 does support DROP COLUMN

public void DeleteColFromTable(String DbName, String TableName, String ColName){
SQLiteDatabase db = openOrCreateDatabase(""+DbName+"", Context.MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS "+TableName+"(1x00dff);");
Cursor c = db.rawQuery("PRAGMA table_info("+TableName+")", null);
if (c.getCount() == 0) {
} else {
String columns1 = "";
String columns2 = "";
while (c.moveToNext()) {
if (c.getString(1).equals(ColName)) {
} else {
columns1 = columns1 + ", " + c.getString(1) + " " + c.getString(2);
columns2 = columns2 + ", " + c.getString(1);
}
if (c.isLast()) {
db.execSQL("CREATE TABLE IF NOT EXISTS DataBackup (" + columns1 + ");");
db.execSQL("INSERT INTO DataBackup SELECT " + columns2 + " FROM "+TableName+";");
db.execSQL("DROP TABLE "+TableName+"");
db.execSQL("ALTER TABLE DataBackup RENAME TO "+TableName+";");
}
}
}
}
and just call a method
DeleteColFromTable("Database name","Table name","Col name which want to delete");

Kotlin solution, based on here , but also:
Ensures the temporary table doesn't already exist
Has a fix of checking the type for the default value, as it returns String type when it's an Integer (reported about this issue here).
Avoids doing anything if the columns that you wish to remove don't exist anyway.
object DbUtil {
/** https://stackoverflow.com/a/51587449/878126 */
#JvmStatic
fun dropColumns(database: SQLiteDatabase, tableName: String,
columnsToRemove: Collection<String>) {
val columnNames: MutableList<String> = ArrayList()
val columnNamesWithType: MutableList<String> = ArrayList()
val primaryKeys: MutableList<String> = ArrayList()
val query = "pragma table_info($tableName);"
val cursor = database.rawQuery(query, null)
val columnDefaultIndex = cursor.getColumnIndex("dflt_value")
val columnNameIndex = cursor.getColumnIndex("name")
val columnTypeIndex = cursor.getColumnIndex("type")
val columnNotNullIndex = cursor.getColumnIndex("notnull")
val columnPrimaryKeyIndex = cursor.getColumnIndex("pk")
val sb = StringBuilder()
var foundColumnsToRemove = false
while (cursor.moveToNext()) {
val columnName = cursor.getString(columnNameIndex)
if (columnsToRemove.contains(columnName)) {
foundColumnsToRemove = true
continue
}
val columnType = cursor.getString(columnTypeIndex)
val isNotNull = cursor.getInt(columnNotNullIndex) == 1
val isPrimaryKey = cursor.getInt(columnPrimaryKeyIndex) == 1
columnNames.add(columnName)
sb.clear()
sb.append("`$columnName` $columnType ")
if (isNotNull)
sb.append(" NOT NULL ")
if (cursor.getType(columnDefaultIndex) != Cursor.FIELD_TYPE_NULL) {
//has default value
when (columnType.uppercase()) {
"INTEGER" -> sb.append(" DEFAULT ${cursor.getInt(columnDefaultIndex)} ")
"TEXT" -> sb.append(" DEFAULT \"${cursor.getString(columnDefaultIndex)}\" ")
"REAL" -> sb.append(" DEFAULT ${cursor.getFloat(columnDefaultIndex)} ")
}
}
columnNamesWithType.add(sb.toString())
if (isPrimaryKey)
primaryKeys.add("`$columnName`")
}
cursor.close()
if (!foundColumnsToRemove)
return
val columnNamesSeparated = TextUtils.join(", ", columnNames)
if (primaryKeys.size > 0)
columnNamesWithType.add("PRIMARY KEY(${TextUtils.join(", ", primaryKeys)})")
val columnNamesWithTypeSeparated = TextUtils.join(", ", columnNamesWithType)
database.beginTransaction()
try {
var newTempTableName: String
var counter = 0
while (true) {
newTempTableName = "${tableName}_old_$counter"
if (!isTableExists(database, newTempTableName))
break
++counter
}
database.execSQL("ALTER TABLE $tableName RENAME TO $newTempTableName;")
database.execSQL("CREATE TABLE $tableName ($columnNamesWithTypeSeparated);")
database.execSQL(
"INSERT INTO $tableName ($columnNamesSeparated) SELECT $columnNamesSeparated FROM $newTempTableName;")
database.execSQL("DROP TABLE ${newTempTableName};")
database.setTransactionSuccessful()
} finally {
database.endTransaction()
}
}
#JvmStatic
fun isTableExists(database: SQLiteDatabase, tableName: String): Boolean {
database.rawQuery(
"select DISTINCT tbl_name from sqlite_master where tbl_name = '$tableName'", null)
?.use {
return it.count > 0
} ?: return false
}
}

You can also now use DB browser for SQLite to manipulate columns

Related

android.database.sqlite.SQLiteException: no such column error even if column exists

I know this question has been asked multiple times, but there is something wrong in my syntax and I can't figure out what. This is the method that adds my column:
Property declaration:
public static final String COLUMN_TS_MILIS = "ts_milis";
public void onCreate(SQLiteDatabase db) {
String query = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +
COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
COLUMN_PRODUCT + " TEXT, " +
COLUMN_PRICE + " TEXT, " +
COLUMN_TS + " TIMESTAMP DEFAULT CURRENT_TIMESTAMP," +
COLUMN_TS_MILIS + "timestamp integer default (cast(strftime('%s', 'now') as int))" +
");";
db.execSQL(query);
and this is the query that triggers the error:
Cursor totalCof = db.rawQuery("SELECT sum(" + COLUMN_PRICE + ")" + " FROM " + TABLE_NAME
+ " WHERE " + COLUMN_TS_MILIS + "= date('now')", null);
What is wrong in my syntax? Many thanks for help!
For the column that is meant to be named as per COLUMN_TS_MILIS, have omitted a space between the column name and the column type and hence the column name is a concatenation of the column name and column type. So assuming COLUMN_TS_MILIS resolves to millis then the QL will be :-
`CREATE TABLE ......,millistimestamp integer default (cast(strftime('%s', 'now') as int))`
instead of
`CREATE TABLE ......,millis timestamp integer default (cast(strftime('%s', 'now') as int))`
Additionally you have specified two types, timestamp and also integer, this won't be an issue SQLIite wise but may lead to confusion.
As such you probably just want
`CREATE TABLE ......,millis integer default (cast(strftime('%s', 'now') as int))`
As such you probably want to use :-
String query = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME + "(" +
COLUMN_ID + " INTEGER PRIMARY KEY, " +
COLUMN_PRODUCT + " TEXT, " +
COLUMN_PRICE + " TEXT, " +
COLUMN_TS + " TIMESTAMP DEFAULT CURRENT_TIMESTAMP," +
COLUMN_TS_MILIS + " INTEGER DEFAULT (cast(strftime('%s', 'now') as int))" +
");";
Note AUTOINCREMENT has been removed as you almost certainly don't need it as it has overheads.
To implement the change, you would have to drop the table, as it exists. The easiest way to do this is to either :-
delete the App's data or
uninstall the App
and then rerun the App (assuming that existing, if any, data can be lost).

Retrieving Int Value from SQLite database

I am trying to retrieve an integer from my SQLite database and my current query crashes my program. This is what I have so far:
*/
public int getWin(String id){
SQLiteDatabase db = this.getWritableDatabase();
String query = "SELECT " + COL3 + " FROM " + TABLE_NAME +
" WHERE " + COL2 + " = '" + id + "'";
Log.d(TAG, "updateName: query: " + query);
db.execSQL(query);
int win = Integer.parseInt(query);
return win;
}
I am not sure why this will not work. Thanks in advance.
You are trying to convert the value SELECT ......... into a number as per int win = Integer.parseInt(query);.
For a SELECT statment you need you need to retrieve a Cursor (result set), via either the query or rawQuery SQLiteDatabase method and then extract the value(s) from the method and to then access the respective column from the respective row(s).
I believe that you would use something like :-
public int getWin(String id){
SQLiteDatabase db = this.getWritableDatabase();
int rv = -1; //<<<<<<<<<< ADDED default value to return if no row found
String query = "SELECT " + COL3 + " FROM " + TABLE_NAME +
" WHERE " + COL2 + " = '" + id + "'";
Log.d(TAG, "updateName: query: " + query);
Cursor csr = db.rawQuery(query,null); //<<<<<<<<<< CHANGED to get the Cursor returned
// ADDED the following IF construct
if (csr.moveToFirst()) {
rv = csr.getInt(csr.getColumnIndex(COL3));
}
//int win = Integer.parseInt(query); //<<<<<<<<<< DELETED (commented out)
csr.close(); //<<<<<<<<<< ADDED should always close a Cursor when done with it
return rv; //<<<<<<<<<< return the value (-1 if no row found)
}
This assumes that you just want the value from a single row as identified by the WHERE clause.
If possible it is recommended to a) not build the query with direct values (makes it vulnerable to SQL Injection) and to b) utilise the convenience query method.
Apply both a and b and your code could be :-
public int getWin(String id){
SQLiteDatabase db = this.getWritableDatabase();
int rv = -1;
String whereclause = COL2 + "=?"; //<<<<<<<<<< where clause without where and ? for value that will be passed
String[] whereargs = new String[]{String.valueOf(id)}; //<<<<<<<<<< arguments used by the whereclause ? replaced on a 1 for 1 basis
String[] columns = new String[]{COL3}; //<<<<<<<<<< the columns to extract as a String array
Cursor csr = db.query(TABLE_NAME,columns,whereclause,whereargs,null,null,null);
if (csr.moveToFirst()) {
rv = csr.getInt(csr.getColumnIndex(COL3));
}
csr.close();
return rv;
}

what is function/value for updating a row with current time_stamp in sqlite

This is my create table statement.
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_BRANDS + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_NAME + " TEXT,"
+ KEY_CREATED_AT + " TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,"
+ KEY_UPDATED_AT + " TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP" + ")";
as per SQLITE document ON UPDATE CURRENT_TIMESTAMP is not allowed in column definition.
so i thought of passing KEY_UPDATED_AT values while updating a row.
This is my update function.
public int updateBrand(Brand brand) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_NAME, brand.getName());
values.put(KEY_UPDATED_AT, ?????)
// updating row
return db.update(TABLE_BRANDS, values, KEY_ID + " = ?",
new String[] { String.valueOf(brand.getId()) });
}
My question is what values should i put values.put(KEY_UPDATED_AT, ?????), to update the row properly.
The ContentValues object allows only literal values.
To do any kind of computation, you must use execSQL instead:
db.execSQL("UPDATE "+TABLE_BRANDS+
" SET "+KEY_NAME+" = ?, "+
KEY_UPDATED_AT+" = CURRENT_TIMESTAMP"+
" WHERE "+KEY_ID+" = ?",
new Object[]{ brand.getName(), brand.getId() });

How to filter data from database based on YYYY-MM using Selection and SelectionArgs[] parameter in Android SQLite Query

I am storing YYYY-MM-DD and HH:MM:SS values in two separate columns in all my SQLite tables.
I have been using the following code to filter data by supplier id and date from my SQLite database.
public double addPurchaseTotal(String supplierID, String date) {
SQLiteDatabase db = helper.getReadableDatabase();
double result = 0;
String selection = VivzHelper.COLUMN_ADD_PURCHASE_SUPPLIER_ID + " =? "
+ " AND " + VivzHelper.COLUMN_ADD_PURCHASE_DATE + " =? ";
String[] selectionArgs = {supplierID, date};
Cursor c = db.query(VivzHelper.ADD_PURCHASE_TABLE,
new String[]{"sum(" + VivzHelper.COLUMN_ADD_PURCHASE_ITEM_COST_PRICE + ")"},
selection,
selectionArgs,
null,
null,
null);
if (c.moveToFirst()) {
result = c.getDouble(0);
}
c.close();
return result;
}
The value for date parameter is obtained from a date picker. As mentioned earlier, date value under the VivzHelper.COLUMN_ADD_PURCHASE_DATE is stored in YYYY-MM-DD format. I would like to filter my data based on YYYY-MM (year and month alone). How can this be done?
Instead of comparing the entire string with =, check for the prefix with LIKE or GLOB:
... WHERE Supplier = 'xxx' AND Date LIKE '2015-04-%'
... WHERE Supplier = 'xxx' AND Date GLOB '2015-04-*'
(GLOB works better together with indexing.)
In Java:
String selection = ...
+ " AND " + VivzHelper.COLUMN_ADD_PURCHASE_DATE + " GLOB ?";
String[] selectionArgs = { ..., date.substring(0, 8) + "*" };
I guess you are looking for this: SQLite Date and Time Functions

Accessing records in Android using rawQuery and then displaying

I am working on several rawQueries to use to parse data from a table in Android. The below code works fine and returns the lowest rowid in the table.
public void firstRecord(View v){
Cursor c = db.rawQuery("SELECT * FROM surveyDB WHERE rowid = (SELECT MIN(rowid) FROM surveyDB)",null);
c.moveToFirst();
szList.add(c.getString(0));
Toast.makeText(getApplicationContext(), "Sucessful Event. szRowid is: " +szList +".", Toast.LENGTH_LONG).show();
}
I have two questions, and they are both extremely basic: 1) what is the best way to expand the above code to create language to capture the contents of other columns in this table at that specific rowid, (rowid, sampler, species, place), and display this in my application? Something like this perhaps:
((EditText)findViewById(R.id.edSpecies)).setText("");
with the proper reference replacing "" in .setText()?
String TABLE_SURVEY = "surveyDB";
String COL_ROW_ID = "rowid";
String COL_SAMPLER = "sampler";
String COL_SPECIES = "species";
String COL_PLACE = "place";
public ArrayList<SurveyRecord> getSurveyRecords()
{
ArrayList<SurveyRecord> records = new ArrayList<SurveyRecord>();
String query = "SELECT * FROM " + TABLE_SURVEY;
query += " WHERE " + COL_ROW_ID = " SELECT MIN ("
query += COL_ROW_ID + ") FROM " + TABLE_SURVEY;
Cursor c = db.rawQuery(query,null);
if(Cursor.moveToFirst())
{
do{
String sampler = c.getString(cursor.getColumnIndex(COL_SAMPLER));
String species= c.getString(cursor.getColumnIndex(COL_SPECIES));
String place = c.getString(cursor.getColumnIndex(COL_PLACE));
String rowId = c.getString(cursor.getColumnIndex(COL_ROW_ID));
records.add(new (rowId,species,place,sampler));
}while(c.moveToNext())
}
c.close();
}
public class SurveyRecord{
String mRowId;
String mSpecies;
String mPlace;
String mSampler;
public SurveyRecord(String rowId,String species,String place,String sampler)
{
this.mRowId = rowId;
this.mSpecies = species;
this.mPlace = place;
this.mSampler = sampler;
}
}
//Goes to the first record in the dataset
public void firstRecord(View v){
Cursor c = db.rawQuery("SELECT * FROM surveyDB WHERE rowid = (SELECT MIN(rowid) FROM surveyDB)",null);
c.moveToFirst();
((EditText)findViewById(R.id.edRowid))
.setText(c.getString(0));
((EditText)findViewById(R.id.edSpecies))
.setText(c.getString(1));
((EditText)findViewById(R.id.edArea))
.setText(c.getString(2));
((EditText)findViewById(R.id.edSampler))
.setText(c.getString(3));
}

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