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HomeDatabaseMysql Tutorialmysql删除字段的方法总结_MySQL

判断字段是否存在的方法总结如下:

1.查找系统表

select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME from information_schema.COLUMNS where COLUMN_NAME='uu';

2.使用describe

describe cdb_posts first

存在第一列返回字段的名称,不存在就返回null,

删除方法:

如果删除的时候涉及的表不多的话,直接:

alter table tb_name drop column col_name;

多的话,可以使用下面的方法:

存储过程删除

DELIMITER $$<br><br>DROP PROCEDURE IF EXISTS `test`.`p_drop_uuid_uuname`$$<br><br>CREATE DEFINER=`root`@`%` PROCEDURE `p_drop_uu`()<br>BEGIN<br>    declare _db_name char(30);<br>    declare _tb_name char(30);<br>    declare _col_name char(30);<br>    declare no_more_row tinyint(1);<br>    <br>    declare cur_uuid cursor for <br>        select TABLE_SCHEMA,TABLE_NAME,COLUMN_NAME <br>            from information_schema.COLUMNS <br>                where COLUMN_NAME='uu';<br>    declare continue handler for not found set no_more_row=1;<br>    set no_more_row=0; -- 判断是否结束的标志位<br>    open cur_uuid;<br>        repeat <br>            fetch cur_uuid into _db_name,_tb_name,_col_name;-- 取记录<br>            -- select _db_name,_tb_name,_col_name;<br>            set @_dt = concat("alter table ", _db_name,".", _tb_name, " drop column uu");<br>            -- 在存储过程中,想把一个变量当作SQL执行,只有用prepare;<br>            prepare s1 from @_dt;<br>            execute s1;<br>            deallocate prepare s1;<br>            until no_more_row<br>        end repeat;<br>    close cur_uuid;<br>    END$$

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