sql ALTER TABLE if列不存在。来自http://stackoverflow.com/questions/24571611/mysql-alter-table-if-column-not

Posted 2021-05-13

SET @preparedStatement = (SELECT IF(
    (SELECT DATA_TYPE
        FROM INFORMATION_SCHEMA.COLUMNS
        WHERE table_schema = 'db_name'
        AND table_name = 'table_name'
        AND column_name = 'column_name'
    ) != 'int',
    "ALTER TABLE `tableName` MODIFY `colName` INT UNSIGNED;",
    "SELECT 1;"
));
PREPARE alterIfNotInt FROM @preparedStatement;
EXECUTE alterIfNotInt;

DEALLOCATE PREPARE alterIfNotInt;

SET @preparedStatement = (SELECT IF(
    (SELECT count(*)
        FROM INFORMATION_SCHEMA.COLUMNS
        WHERE table_schema = 'db_name'
        AND table_name = 'table_name'
        AND column_name = 'column_name'
    ) > 0,
    "SELECT 1;",
    "ALTER TABLE `tableName` ADD `colName` TINYINT(1) NULL DEFAULT '0';"
));
PREPARE alterIfNotExists FROM @preparedStatement;
EXECUTE alterIfNotExists;

DEALLOCATE PREPARE alterIfNotExists;