I want to insert a record into a sqlite table if its actually not inserted.
Let's say it has three fields pk, name, address
I want to INSERT new record with name if that name not added preveously.
Can we do with this in a single Query. Seems like its slightly different from SQL Queries sometimes.
Yes, you can do that with a single query.
INSERT ON CONFLICT IGNORE should help you: http://www.sqlite.org/lang_conflict.html
Put a unique key on the name, this will create a conflict when you try inserting a record if the name already exists.
The default is ABORT, so without the IGNORE, the statement will return an error. If you don't want that, use IGNORE.
If you can't make use of a UNIQUE INDEX in combination with INSERT INTO or INSERT OR IGNORE INTO, you could write a query like this;
INSERT INTO table (column)
SELECT value
WHERE NOT EXISTS (SELECT 1
FROM table
WHERE column = value)
Related
I feel like this should be easy...
I have a table like this:
CREATE TABLE table_name (
id INTEGER PRIMARY KEY,
name TEXT NOT NULL,
UNIQUE (name COLLATE NOCASE)
)
No two names are the same, case insensitive. Right now I have users adding names and it does this:
INSERT INTO table_name (name) VALUES ("my name");
And I need to get the id of the row, which is easy with PHP PDO's lastInsertID(). But I also want, if the user is adding a name that's already in the database, for nothing to be added to the database, but still get that id without having to do another database call. I was hoping for something like
INSERT OR REPLACE INTO table_name (name) VALUES ("my name");
And have it just overwrite the same data into the cell and return the lastInsertID (even though it wasn't inserted?). But that doesn't work. What are my other options? Will I have to do a separate database query to see if the name field already exists?
With the OR REPLACE clause, the statement always deletes any old row.
Just use two statements. (There is no technical reason for doing this in a single statement.)
I'm using Sqlite and I found out that INSERT does not return the just inserted record with the automatically created primary key.
To solve this issue I found out I can use SELECT last_insert_rowid(). This returns the value that I need.
I need this value to update a field in the record of my database.
Is there any way I could form a SELECT query that has the result of that query built in?
UPDATE events SET url='query executed' WHERE eventId = <value of above query should come here>
If SELECT last_insert_rowid() returns the value that you need then put it there as a subquery. Subquery must be in (your_subquery) brackets.
I use a database in my project and when i insert values into a table i need to check if the field already has a value that does not produce an insert.
for exemple:
INSERT INTO myTable (column1) values ('some_value1')
if some_value1 alredy exists in column1 do not insert the value.
Put a unique constraint on myTable.column1. Then, whenever you try to insert a duplicate value, it won't let you as it violates the constraint. You can either catch and handle this error, or just let the DB engine do it's thing automatically.
EDIT: Note that SQLite doesn't allow you to do many alterations to your table, once it's created; so you may have to recreate your table with the constraint in place.
I believe this can be handled using the conflict resolution IGNORE method on SQLite. The code below should do the trick. The column1 here should be set to unique for this.
INSERT OR IGNORE INTO myTable (column1) values ('some_value1')
I'm using the following links for reference;
http://www.sqlite.org/lang_insert.html
http://www.sqlite.org/lang_conflict.html
Maybe i should do this in C# but i have more then one row with linkId X. I would like to remove it but i am unsure how. In code i could just use a foreach from 0 to n and remove any found rows with a greater (or !=) id but thats in code. Is there a less difficult way of doing it using sqlite?
Assuming the table's name is tableName and there is a primary key field named id, the following sql would do it. I think the following SQL query is general enough and should be able to be executed under any database engine.
delete from tableName
where id not in (
select min(id) from tableName
group by linkId
)
I've never seen the syntax INSERT OR REPLACE INTO names (id, name) VALUES (1, "John") used in SQL before, and I was wondering why it's better than UPDATE names SET name = "John" WHERE id = 1. Is there any good reason to use one over the other. Is this syntax specific to SQLite?
UPDATE will not do anything if the row does not exist.
Where as the INSERT OR REPLACE would insert if the row does not exist, or replace the values if it does.
Another fact to notice: INSERT OR REPLACE will replace any values not supplied in the statement.
For instance if your table contains a column "lastname" which you didn't supply a value for, INSERT OR REPLACE will nullify the "lastname" if possible (if constraints allow it), or fail.
REPLACE INTO table(column_list) VALUES(value_list);
is a shorter form of
INSERT OR REPLACE INTO table(column_list) VALUES(value_list);
For REPLACE to execute correctly your table structure must have unique rows, whether a simple primary key or a unique index.
REPLACE deletes, then INSERTs the record and will cause an INSERT Trigger to execute if you have them setup. If you have a trigger on INSERT, you may encounter issues.
This is a work around.. not checked the speed..
INSERT OR IGNORE INTO table (column_list) VALUES(value_list);
followed by
UPDATE table SET field=value,field2=value WHERE uniqueid='uniquevalue'
This method allows a replace to occur without causing a trigger.
The insert or replace query would insert a new record if id=1 does not already exist.
The update query would only oudate id=1 if it aready exist, it would not create a new record if it didn't exist.