mysql 修改表结构脚本

参考 http://stackoverflow.com/questions/972922/add-column-to-mysql-table-if-it-does-not-exist
DELIMITER $$

DROP PROCEDURE IF EXISTS addFieldIfNotExists

$$

DROP FUNCTION IF EXISTS isFieldExisting

$$

CREATE FUNCTION isFieldExisting (schema_name_IN VARCHAR(100), table_name_IN VARCHAR(100), field_name_IN VARCHAR(100))

RETURNS INT

RETURN (

SELECT COUNT(COLUMN_NAME)

FROM INFORMATION_SCHEMA.columns

WHERE TABLE_SCHEMA = schema_name_IN

AND TABLE_NAME = table_name_IN

AND COLUMN_NAME = field_name_IN

)

$$

CREATE PROCEDURE addFieldIfNotExists (

IN schema_name_IN VARCHAR(100),

IN table_name_IN VARCHAR(100),

IN field_name_IN VARCHAR(100),

IN field_definition_IN VARCHAR(100)

)

BEGIN

SET @isFieldThere = isFieldExisting(schema_name_IN, table_name_IN, field_name_IN);

IF (@isFieldThere = 0) THEN

SET @ddl = CONCAT('ALTER TABLE ', table_name_IN);

SET @ddl = CONCAT(@ddl, ' ', 'ADD COLUMN') ;

SET @ddl = CONCAT(@ddl, ' ', field_name_IN);

SET @ddl = CONCAT(@ddl, ' ', field_definition_IN);

PREPARE stmt FROM @ddl;

EXECUTE stmt;

DEALLOCATE PREPARE stmt;

END IF;

END;

$$

-- 测试表

CREATE TABLE `mytbl` (

`c1` INT(11) NULL DEFAULT NULL,

`c2` INT(11) NULL DEFAULT NULL,

`c3` INT(11) NULL DEFAULT NULL

)

ENGINE=MyISAM;

CALL addFieldIfNotExists ('vnap_user', 'mytbl', 'c1_1', 'INT(11) NULL DEFAULT NULL AFTER `c1`');

CALL addFieldIfNotExists ('vnap_user', 'mytbl', 'c2_1', 'INT(11) NULL DEFAULT NULL AFTER `c2`');

CALL addFieldIfNotExists ('vnap_user', 'mytbl', 'c3_1', 'INT(11) NULL DEFAULT NULL AFTER `c3`');