sql可重复执行语句例子

1.添加字段

SET @add__on_admin = (SELECT IF(
(SELECT count(1)
FROM INFORMATION_SCHEMA.COLUMNS
WHERE table_name = 'admin'
AND table_schema = DATABASE()
AND column_name = 'lft'
) > 0,
"select 'admin exist lft'",
"alter table admin add column lft int(11) unsigned COMMENT '树形结构使用'; "
));
PREPARE stmt FROM @add_lft_on_admin;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

-- 可重复性添加索引

DROP PROCEDURE IF EXISTS add_index_to_macc_stalog_1;
DELIMITER //
CREATE PROCEDURE add_index_to_macc_stalog_1() BEGIN
DECLARE CurrentDatabase VARCHAR(250);
SELECT DATABASE() INTO CurrentDatabase;
IF NOT EXISTS (SELECT * FROM information_schema.statistics WHERE table_schema=CurrentDatabase AND table_name = 'macc_stalog_1' AND index_name = 'idx_ssid') THEN
ALTER TABLE `macc_stalog_1` ADD INDEX idx_ssid ( `ssid` );
ELSE
select "macc_stalog_1 is already exist idx_ssid";
END IF;
END//
DELIMITER ;
CALL add_index_to_macc_stalog_1();
DROP PROCEDURE IF EXISTS add_index_to_macc_stalog_1;