Question

DELIMITER $$
CREATE TRIGGER t1_trigger BEFORE DELETE ON  t1
FOR EACH ROW
BEGIN

-- Declaration
    DECLARE str VARCHAR(1024) DEFAULT "";
    DECLARE c1 VARCHAR(64) DEFAULT "";
    DECLARE c2 VARCHAR(64) DEFAULT "";
    DECLARE c3 VARCHAR(64) DEFAULT "";
    DECLARE x int ;
    DECLARE var VARCHAR(64) DEFAULT "var";
    DECLARE i_counter INT DEFAULT 1;

-- Find the number of columns of a table.
DECLARE cur1 CURSOR FOR select count(*) from information_schema.columns where table_schema='plsqls' and table_name='t1';

-- Get the Column values of table
DECLARE cur CURSOR FOR SELECT * FROM t1 WHERE t1.id =     OLD.ID;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

-- Create Dynamic Variables of a table
OPEN cur1;
     FETCH cur1 INTO x;   
         while i_counter < x DO
            SET str =CONCAT(str,CONCAT(var,i_counter,','));
            SET i_counter=i_counter+1;
         end while;
CLOSE cur1;  

-- Assign the coulmn values to the dynamic variables.
-- Here i get the column names instead of column values.
OPEN cur;
    ins_loop: LOOP
        FETCH cur INTO str;
        IF done THEN
            LEAVE ins_loop;
        END IF;          
        INSERT INTO t1_log VALUES (null, str);
    END LOOP;
   CLOSE cur; 
 END;$$

问题：
这里的问题我们不能发现＆＃39; str＆＃39;动态应用。
当我删除表格（t1）但我面对下面的错误是＆＃39;错误的FETCH变量数量＆＃39;。 -

Answer 1

您得到的错误是'FETCH变量数不正确'。
这是因为您选择表t1中的所有列作为
DECLARE cur CURSOR FOR SELECT * FROM t1 WHERE t1.id = OLD.ID;）
但只取1个值作为
FETCH cur INTO str;

解决方案

使用光标选择所需的列为
DECLARE cur CURSOR FOR SELECT id FROM t1 WHERE t1.id = OLD.ID;

或

获取您选择的所有列为
FETCH cur INTO x, y, z;

Mysql动态地从游标中获取值

1 个答案: