call modify_collation(@num,@count_num)
> 1146 - Table 'test.table_name' doesn't exist
> 时间: 0.009s我在使用mysql存储过程时，打印时游标取值为空，报错找不到表。我的过程语句是这样的：
drop procedure if exists modify_collation;DELIMITER //
create PROCEDURE modify_collation(out origin_num int(10),out count_num int(10))
COMMENT 'modify_collation'
SQL SECURITY DEFINER
BEGINDECLARE table_name VARCHAR(100);declare column_name VARCHAR(100);declare done int(10) default 0;declare collation_cursor cursor for SELECT table_name, column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'test' and collation_name = 'utf8mb4_0900_ai_ci';declare continue handler for not found set done = 1;select count(1) into origin_num from INFORMATION_SCHEMA.COLUMNSWHERE TABLE_SCHEMA = 'test' and collation_name = 'utf8mb4_0900_ai_ci';select origin_num;open collation_cursor ;set count_num := 0;mylp:loopFETCH collation_cursor into table_name,column_name;select table_name,column_name;ALTER TABLE table_name MODIFY column_name VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;if done = 1 thenleave mylp;end if;set count_num := count_num +1;end loop;close collation_cursor;select count_num;
end//
DELIMITER ;
执行了几遍，进入了loop循环，总是打印游标取值为空：
我执行定义游标时后面的 select 语句也能查询到数据，
SELECT table_name, column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'test' and collation_name = 'utf8mb4_0900_ai_ci';
最后发现，我定义的变量名字和查询的字段名字一样，所以单独查询sql的时候有数据，执行存储过程时，select后面查询的是变量，而不是表中的字段，变量没有赋值就查询的是空。
把定义的变量名字修改后，就正常了。
drop procedure if exists modify_collation;DELIMITER //
create PROCEDURE modify_collation(out origin_num int(10),out count_num int(10))
COMMENT 'modify_collation'
SQL SECURITY DEFINER
BEGINDECLARE t_name VARCHAR(100);declare c_name VARCHAR(100);declare done int(10) default 0;declare collation_cursor cursor for SELECT table_name, column_name FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'test' and collation_name = 'utf8mb4_0900_ai_ci';declare continue handler for not found set done = 1;select count(1) into origin_num from INFORMATION_SCHEMA.COLUMNSWHERE TABLE_SCHEMA = 'test' and collation_name = 'utf8mb4_0900_ai_ci';select origin_num;open collation_cursor ;set count_num := 0;mylp:loopFETCH collation_cursor into t_name,c_name;select t_name,c_name;
-- ALTER TABLE t_name MODIFY c_name VARCHAR(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;if done = 1 thenleave mylp;end if;set count_num := count_num +1;end loop;close collation_cursor;select count_num;
end//
DELIMITER ;
