I am using SQLite3 with Python. I am quite certain that the 'WHERE' clause does not work with 'INSERT' operation, but I really need to have a workaround to solve my issue. I have the following prepopulated database:
I was hoping to come up with an SQL statement where I can add the VALUES ('2021-01-13', '36.8') to the table WHERE family='FAA' AND model='MAA'. I have read a lot of stuff online but still no luck on my side.
I think you want an update here:
UPDATE yourTable
SET date = '2021-01-13', duration = 36.8
WHERE family = 'FAA' AND model = 'MAA';
You want to update your table, insert is only for new rows. When you want to change a value, you must to use update statement.
UPDATE table_name
SET date = '2021-01-13', duration = '36.8'
WHERE family='FAA' AND model='MAA';
https://www.sqlite.org/lang_update.html
I'm converting a FoxPro database to SQLite, and migrating the instructions to update, where I found a problem.
If inside FoxPro I use Update Fact01 set Motivo = 'asdfgh' where TipoDoc='FV'
the rows are not updated.
But if I use Update Fact01 set Motivo = 'asdfgh' where TipoDoc Like 'FV' the rows are changed.
If I do the first instruction inside the SQLite engine, the rows are also changed. The field type for TipoDoc is NChar(2).
Also, If i do a select * from Fact01 where TipoDoc ='FV' statement inside Foxpro it works OK.
Any idea what's happening here?
I'm not sure if it's due to the fact that Nchar can store unicode data or the way data in general is stored. Wrapping an ALLTRIM around the WHERE clause may correct the problem.
Update Fact01 set Motivo = 'asdfgh' where ALLTRIM(TipoDoc)='FV'
This happened to me because i stored the column value as a BLOB instead of TEXT. Turns out the BLOB value is less than a TEXT value so LIKE found matches but = did not. you might be having the same issue.
I have a source and a target table. I need to make update and insert together in final table with following conditions:
1) When SourceTable.ProductName = TargetTable.ProductName and SourceTable.Amount = TargetTable.Amount Then
Update TargetTable set TargetTable.ValidFrom = sysdate
Also i need to insert like this,
Insert Into TargetTable(ProductName,Amount,ValidFrom,Version) Values(TargetTable.ProductName,TargetTable.Amount, sysdate, TargetTable.Version + 1)
This is to maintain version.
2) When there is no match then i need to insert directly like this,
Insert Into TargetTable(ProductName,Amount,ValidFrom,Version) Values(SourceTable.ProductName,SourceTable.Amount, sysdate,1)
As of now i am thinking of capturing these matching records in a Cursor and perform Update and Insert together in cursor loop. But i am willing to avoid loops a i have approx 10 millions of matching records.
We also have Merge statement, but I believe Merge do not support Update and Insert together in single "WHEN MATCHED" Clause. Please correct me if i am wrong?
Kindly suggest the best way to achieve this behavior.
SQLite doesn't support updates with joins. (see this closely related SO question)
Let's say I have a table data with these columns:
INTEGER id
TEXT foo
TEXT bar
TEXT baz
and I have another table selection with one column INTEGER id.
What I would like to do is given an integer id srcID, to copy the foo and bar values from the data row src to the data rows where the ids match the selection table.
In "standard" SQL (or at least the MySQL variant), this is something like
UPDATE data, selection, data as src
SET data.foo = src.foo, data.bar = src.bar
WHERE data.id = selection.id
AND src.id = ?
(? = prepared statement value set to srcID)
Any suggestions?
Last time I used Oracle, I don't think it supported your syntax either.
I don't see how you could do that with a single SQL command in SQLite, but have you looked into using an UPDATE trigger on the data table?
I would need to rename a few columns in some tables in a SQLite database.
I know that a similar question has been asked on stackoverflow previously, but it was for SQL in general, and the case of SQLite was not mentioned.
From the SQLite documentation for ALTER TABLE, I gather that it's not possible to do such a thing "easily" (i.e. a single ALTER TABLE statement).
I was wondering someone knew of a generic SQL way of doing such a thing with SQLite.
Note that as of version 3.25.0 released September 2018 you can now use ALTER TABLE to rename a column.
Example to rename Really Bad : Column Name to BetterColumnName:
ALTER TABLE your_table
RENAME COLUMN "Really Bad : Column Name" TO BetterColumnName
According to keywords the use of "double-quotes" is the standard way
Original "create new and drop old table" answer below.
Say you have a table and need to rename "colb" to "col_b":
First create the new table with a temporary name, based on the old table definition but with the updated column name:
CREATE TABLE tmp_table_name (
col_a INT
, col_b INT
);
Then copy the contents across from the original table.
INSERT INTO tmp_table_name(col_a, col_b)
SELECT col_a, colb
FROM orig_table_name;
Drop the old table.
DROP TABLE orig_table_name;
Last you rename the temporary table table to the original:
ALTER TABLE tmp_table_name RENAME TO orig_table_name;
Don't forget to re-create indexes, triggers, etc. The documentation gives a fuller picture of the gotchas and caveats.
Wrapping all this in a BEGIN TRANSACTION; and COMMIT; is also probably a good idea.
This was just fixed with 2018-09-15 (3.25.0)
Enhancements the ALTER TABLE command:
Add support for renaming columns within a table using ALTER TABLE table RENAME COLUMN oldname TO newname.
Fix table rename feature so that it also updates references to the renamed table in triggers and views.
You can find the new syntax documented under ALTER TABLE
The RENAME COLUMN TO syntax changes the column-name of table table-name into new-column-name. The column name is changed both within the table definition itself and also within all indexes, triggers, and views that reference the column. If the column name change would result in a semantic ambiguity in a trigger or view, then the RENAME COLUMN fails with an error and no changes are applied.
Image source: https://www.sqlite.org/images/syntax/alter-table-stmt.gif
Example:
CREATE TABLE tab AS SELECT 1 AS c;
SELECT * FROM tab;
ALTER TABLE tab RENAME COLUMN c to c_new;
SELECT * FROM tab;
db-fiddle.com demo
Android Support
As of writing, Android's API 27 is using SQLite package version 3.19.
Based on the current version that Android is using and that this update is coming in version 3.25.0 of SQLite, I would say you have bit of a wait (approximately API 33) before support for this is added to Android.
And, even then, if you need to support any versions older than the API 33, you will not be able to use this.
Digging around, I found this multiplatform (Linux | Mac | Windows) graphical tool called DB Browser for SQLite that actually allows one to rename columns in a very user friendly way!
Edit | Modify Table | Select Table | Edit Field. Click click! Voila!
However, if someone want to share a programmatic way of doing this, I'd be happy to know!
While it is true that there is no ALTER COLUMN, if you only want to rename the column, drop the NOT NULL constraint, or change the data type, you can use the following set of commands:
Note: These commands have the potential to corrupt your database, so make sure you have a backup
PRAGMA writable_schema = 1;
UPDATE SQLITE_MASTER SET SQL = 'CREATE TABLE BOOKS ( title TEXT NOT NULL, publication_date TEXT)' WHERE NAME = 'BOOKS';
PRAGMA writable_schema = 0;
You will need to either close and reopen your connection or vacuum the database to reload the changes into the schema.
For example:
Y:\> sqlite3 booktest
SQLite version 3.7.4
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> create table BOOKS ( title TEXT NOT NULL, publication_date TEXT NOT NULL);
sqlite> insert into BOOKS VALUES ("NULLTEST",null);
Error: BOOKS.publication_date may not be NULL
sqlite> PRAGMA writable_schema = 1;
sqlite> UPDATE SQLITE_MASTER SET SQL = 'CREATE TABLE BOOKS ( title TEXT NOT NULL, publication_date TEXT)' WHERE NAME = 'BOOKS';
sqlite> PRAGMA writable_schema = 0;
sqlite> .q
Y:\> sqlite3 booktest
SQLite version 3.7.4
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> insert into BOOKS VALUES ("NULLTEST",null);
sqlite> .q
REFERENCES FOLLOW:
pragma writable_schema
When this pragma is on, the SQLITE_MASTER tables in which database can be changed using ordinary UPDATE, INSERT, and DELETE statements. Warning: misuse of this pragma can easily result in a corrupt database file.
alter table
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.
Recently I had to do that in SQLite3 with a table named points with the colunms id, lon, lat. Erroneusly, when the table was imported, the values for latitude where stored in the lon column and viceversa, so an obvious fix would be to rename those columns. So the trick was:
create table points_tmp as select id, lon as lat, lat as lon from points;
drop table points;
alter table points_tmp rename to points;
I hope this would be useful for you!
CASE 1 : SQLite 3.25.0+
Only the Version 3.25.0 of SQLite supports renaming columns. If your device is meeting this requirement, things are quite simple. The below query would solve your problem:
ALTER TABLE "MyTable" RENAME COLUMN "OldColumn" TO "NewColumn";
CASE 2 : SQLite Older Versions
You have to follow a different Approach to get the result which might be a little tricky
For example, if you have a table like this:
CREATE TABLE student(Name TEXT, Department TEXT, Location TEXT)
And if you wish to change the name of the column Location
Step 1: Rename the original table:
ALTER TABLE student RENAME TO student_temp;
Step 2: Now create a new table student with correct column name:
CREATE TABLE student(Name TEXT, Department TEXT, Address TEXT)
Step 3: Copy the data from the original table to the new table:
INSERT INTO student(Name, Department, Address) SELECT Name, Department, Location FROM student_temp;
Note: The above command should be all one line.
Step 4: Drop the original table:
DROP TABLE student_temp;
With these four steps you can manually change any SQLite table.
Keep in mind that you will also need to recreate any indexes, viewers or triggers on the new table as well.
Quoting the sqlite documentation:
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 colum, remove a column, or add or remove constraints from a table.
What you can do of course is, create a new table with the new layout, SELECT * FROM old_table, and fill the new table with the values you'll receive.
First off, this is one of those things that slaps me in the face with surprise: renaming of a column requires creating an entirely new table and copying the data from the old table to the new table...
The GUI I've landed on to do SQLite operations is Base. It's got a nifty Log window that shows all the commands that have been executed. Doing a rename of a column via Base populates the log window with the necessary commands:
These can then be easily copied and pasted where you might need them. For me, that's into an ActiveAndroid migration file. A nice touch, as well, is that the copied data only includes the SQLite commands, not the timestamps, etc.
Hopefully, that saves some people time.
change table column < id > to < _id >
String LastId = "id";
database.execSQL("ALTER TABLE " + PhraseContract.TABLE_NAME + " RENAME TO " + PhraseContract.TABLE_NAME + "old");
database.execSQL("CREATE TABLE " + PhraseContract.TABLE_NAME
+"("
+ PhraseContract.COLUMN_ID + " INTEGER PRIMARY KEY,"
+ PhraseContract.COLUMN_PHRASE + " text ,"
+ PhraseContract.COLUMN_ORDER + " text ,"
+ PhraseContract.COLUMN_FROM_A_LANG + " text"
+")"
);
database.execSQL("INSERT INTO " +
PhraseContract.TABLE_NAME + "("+ PhraseContract.COLUMN_ID +" , "+ PhraseContract.COLUMN_PHRASE + " , "+ PhraseContract.COLUMN_ORDER +" , "+ PhraseContract.COLUMN_FROM_A_LANG +")" +
" SELECT " + LastId +" , "+ PhraseContract.COLUMN_PHRASE + " , "+ PhraseContract.COLUMN_ORDER +" , "+ PhraseContract.COLUMN_FROM_A_LANG +
" FROM " + PhraseContract.TABLE_NAME + "old");
database.execSQL("DROP TABLE " + PhraseContract.TABLE_NAME + "old");
Create a new column with the desired column name: COLNew.
ALTER TABLE {tableName} ADD COLUMN COLNew {type};
Copy contents of old column COLOld to new column COLNew.
INSERT INTO {tableName} (COLNew) SELECT {COLOld} FROM {tableName}
Note: brackets are necessary in above line.
As mentioned before, there is a tool SQLite Database Browser, which does this. Lyckily, this tool keeps a log of all operations performed by the user or the application. Doing this once and looking at the application log, you will see the code involved. Copy the query and paste as required. Worked for me. Hope this helps
From the official documentation
A simpler and faster procedure can optionally be used for some changes that do no affect the on-disk content in any way. The following simpler procedure is appropriate for removing CHECK or FOREIGN KEY or NOT NULL constraints, renaming columns, or adding or removing or changing default values on a column.
Start a transaction.
Run PRAGMA schema_version to determine the current schema version number. This number will be needed for step 6 below.
Activate schema editing using PRAGMA writable_schema=ON.
Run an UPDATE statement to change the definition of table X in the sqlite_master table: UPDATE sqlite_master SET sql=... WHERE type='table' AND name='X';
Caution: Making a change to the sqlite_master table like this will render the database corrupt and unreadable if the change contains a syntax error. It is suggested that careful testing of the UPDATE statement be done on a separate blank database prior to using it on a database containing important data.
If the change to table X also affects other tables or indexes or triggers are views within schema, then run UPDATE statements to modify those other tables indexes and views too. For example, if the name of a column changes, all FOREIGN KEY constraints, triggers, indexes, and views that refer to that column must be modified.
Caution: Once again, making changes to the sqlite_master table like this will render the database corrupt and unreadable if the change contains an error. Carefully test of this entire procedure on a separate test database prior to using it on a database containing important data and/or make backup copies of important databases prior to running this procedure.
Increment the schema version number using PRAGMA schema_version=X where X is one more than the old schema version number found in step 2 above.
Disable schema editing using PRAGMA writable_schema=OFF.
(Optional) Run PRAGMA integrity_check to verify that the schema changes did not damage the database.
Commit the transaction started on step 1 above.
One option, if you need it done in a pinch, and if your initial column was created with a default, is to create the new column you want, copy the contents over to it, and basically "abandon" the old column (it stays present, but you just don't use/update it, etc.)
ex:
alter table TABLE_NAME ADD COLUMN new_column_name TYPE NOT NULL DEFAULT '';
update TABLE_NAME set new_column_name = old_column_name;
update TABLE_NAME set old_column_name = ''; -- abandon old column, basically
This leaves behind a column (and if it was created with NOT NULL but without a default, then future inserts that ignore it might fail), but if it's just a throwaway table, the tradeoffs might be acceptable. Otherwise use one of the other answers mentioned here, or a different database that allows columns to be renamed.
need to rename a few columns in some tables
Another way is to use multiple SQLite3 commands to "rename" a column,
in "some" tables, repeat as needed:
.output tmp
SELECT "ALTER TABLE """|| sqlite_master.name ||""" RENAME COLUMN old_name TO new_name;" FROM sqlite_master
WHERE type = "table" AND sqlite_master.name NOT LIKE 'sqlite_%';
.read tmp
source
Since version 2018-09-15 (3.25.0)
sqlite supports renaming columns
https://sqlite.org/changes.html
sqlite3 yourdb .dump > /tmp/db.txt
edit /tmp/db.txt change column name in Create line
sqlite2 yourdb2 < /tmp/db.txt
mv/move yourdb2 yourdb