Question

I want to update and select one row within one query in SqLite. In MySql my wanted query would look like this:

SET @update_id := -1;
UPDATE data SET `Status` = 'running', Id = (SELECT @update_id := Id) 
  WHERE `Status` = 'scheduled' LIMIT 1;
SELECT * FROM data WHERE id=@update_id;"

The above query will set the Status to ‘running’ and the value of the variable @update_id to the Id of the modified row for the first row that is having Status of ‘scheduled’ and than uses the variable @update_id to fetch the complete modified row.

The important point is that I need to select the row that I had been modified by the UPDATE statement

But as far as I know SqLite does not support variables.

How can the MySQL query from above be rewritten for SqLite?

Answer 1

You need to declare and use variables in whatever program you write that runs SQLite statements.

Thankfully, you can use bind variables in SQLite:

//1.  Fetch the id into whatever language you are using:
SELECT id FROM DATA WHERE status = 'scheduled' LIMIT 1;

//2. Retrieve the id value from Step 1's resultset
int id = [id value from the resultset];

//3. Construct the update statement
parsed_sql_stmt stmt = parse_sql(UPDATE DATA SET STATUS = 'running' WHERE ID = ?);

//4. Execute update statement
exec_stmt(stmt, id);

//5. Select everything in the DATA table for that record
stmt = parse_sql(SELECT * FROM DATA WHERE id = ?);
exec_stmt(stmt, id);

sheepsimulator is right – this is three separate statements.