Preparing a MySQL INSERT/UPDATE statement with DEFAULT values

后端 未结 4 1694
谎友^
谎友^ 2020-12-06 10:38

Quoting MySQL INSERT manual - same goes for UPDATE:

Use the keyword DEFAULT to set a column explicitly to its default value. This makes it easier to w

4条回答
  •  甜味超标
    2020-12-06 11:05

    I tried replying to VolkerK answer, but couldnt find how. :( I'm kinda new to all this.

    Anyway, I created a mysql function to use in conjuction with his COALESCE idea

    CREATE FUNCTION NULLDEFAULT(colname VARCHAR(64), tablename VARCHAR(64), dbname VARCHAR(64)) RETURNS longtext DETERMINISTIC READS SQL DATA
    BEGIN
        DECLARE retval longtext;
        SELECT
            COLUMN_DEFAULT INTO retval 
        FROM
            information_schema.COLUMNS
        WHERE
            TABLE_NAME = tablename
        AND
            COLUMN_NAME = colname
        AND
            TABLE_SCHEMA = dbname;
    
        RETURN retval;
    END
    

    You would use it like this:

    $stmt = $pdo->prepare("
      INSERT INTO
        foo
        (x,y,z)
      VALUES
        (
          Coalesce(:x, NULLDEFAULT('x', 'foo', 'database')),
          Coalesce(:y, NULLDEFAULT('y', 'foo', 'database')),
          Coalesce(:z, NULLDEFAULT('z', 'foo', 'database'))
        )
    ");
    

    That will return null if the column has no default value, and won't trigger the "Column has no default value" Error.

    Of course you could modify it to not require the database parameter

提交回复
热议问题