Mysql 在存储过程中替换变量和游标的问题
所以我知道为了替换select语句中的游标,我们需要在prepare语句之前定义它。我可以在那个里替换变量,但对于游标,我有一个相同的问题 例如,下面的语句应该正确地替换表的变量值,并且应该创建一个表作为试验数据Mysql 在存储过程中替换变量和游标的问题,mysql,loops,variables,stored-procedures,cursor,Mysql,Loops,Variables,Stored Procedures,Cursor,所以我知道为了替换select语句中的游标,我们需要在prepare语句之前定义它。我可以在那个里替换变量,但对于游标,我有一个相同的问题 例如,下面的语句应该正确地替换表的变量值,并且应该创建一个表作为试验数据 SET @user := 'trial'; SET @group := 'data'; SET @table := CONCAT(@user, '_', @group); SET @stat = CONCAT('CREATE TABLE ',@table,' as SELECT @us
SET @user := 'trial';
SET @group := 'data';
SET @table := CONCAT(@user, '_', @group);
SET @stat = CONCAT('CREATE TABLE ',@table,' as SELECT @user, @group;');
PREPARE stmt from @stat;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;
然而,当我试图在带有游标的存储过程中应用相同的逻辑时,我遇到了如下错误-
01:13:52 call cursor_ROWPERROW() Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'NULL' at line 1 0.000 sec
在这个场景中,我试图通过替换variable和cursor的值来动态创建表。在这里,我试图基于我从信息模式中标识的另一个表中的相同列,动态创建PD_yyyy_uyx表
DROP PROCEDURE IF EXISTS cursor_ROWPERROW;
DELIMITER $$
CREATE PROCEDURE cursor_ROWPERROW()
BEGIN
DECLARE cursor_COL VARCHAR(50);
DECLARE cursor_TAB VARCHAR(50);
DECLARE tab VARCHAR(100);
DECLARE col1 VARCHAR(50);
DECLARE col2 VARCHAR(50);
DECLARE done INT DEFAULT 0;
DECLARE cursor_i CURSOR FOR SELECT COLUMN_NAME, TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='xxxxx' AND TABLE_NAME='yyyyy' AND COLUMN_NAME = 'zzzzz';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cursor_i;
read_loop: LOOP
FETCH cursor_i INTO cursor_COL, cursor_TAB;
SET tab := CONCAT('PD', '_', @cursor_TAB, '_' , @cursor_COL);
SET col1 := CONCAT(@cursor_COL);
SET col2 := CONCAT(@cursor_COL, '_', 'value');
IF done THEN
LEAVE read_loop;
END IF;
SET @dyn_sql := CONCAT('CREATE TABLE ',@tab,' AS SELECT Codevalue as ',@col1,', valueLabel as ',@col2,' from valuesets14 where varName = cursor_COL and TableName = cursor_TAB;');
PREPARE stmt_dyn_view FROM @dyn_sql;
EXECUTE stmt_dyn_view;
DEALLOCATE PREPARE stmt_dyn_view;
END LOOP;
CLOSE cursor_i;
END;
$$
DELIMITER ;
尽管我用下面的select语句替换了整个SET@dyn_sql块,但它运行良好,并提供了我想要为其创建多个表的确切数据集。请注意,我正在引用的表中没有一个值为NULL,因此我似乎缺少一些游标替换
SELECT Codevalue as ',@col1,', valueLabel as ',@col2,' from valuesets14 where varName = cursor_COL and TableName = cursor_TAB;
有谁能帮我弄清楚这个问题吗?问题是你混淆了引用变量的各种方式。在声明@符号时应忽略它们
read_loop: LOOP
FETCH cursor_i INTO cursor_COL, cursor_TAB;
SET tab := CONCAT('PD', '_', cursor_TAB, '_' , cursor_COL);
SET col1 := CONCAT(cursor_COL);
SET col2 := CONCAT(cursor_COL, '_', 'value');
IF done THEN
LEAVE read_loop;
END IF;
SET @dyn_sql := CONCAT('CREATE TABLE ',tab,' AS SELECT Codevalue as ',col1,', valueLabel as ',col2,' from valuesets14 where varName = cursor_COL and TableName = cursor_TAB;');
PREPARE stmt_dyn_view FROM @dyn_sql;
EXECUTE stmt_dyn_view;
DEALLOCATE PREPARE stmt_dyn_view;
END LOOP;
谢谢你的想法,奈杰尔,但是,我还是遇到了另一个问题,游标变量替换,它抱怨
call cursor_ROWPERROW(): Error Code: 1054. Unknown column 'zzzzz' in 'where clause'
因此,基本上,它无法替换光标值,所以我采用了与您提到的相同的方法,在文本中加上引号,因此使用select query来查看它试图生成的查询,我使用了下面的SQL解决了我的问题
DROP PROCEDURE IF EXISTS cursor_ROWPERROW;
DELIMITER $$
CREATE PROCEDURE cursor_ROWPERROW()
BEGIN
DECLARE cursor_COL VARCHAR(50);
DECLARE cursor_TAB VARCHAR(50);
DECLARE tab VARCHAR(100);
DECLARE col1 VARCHAR(50);
DECLARE col2 VARCHAR(50);
DECLARE done INT DEFAULT 0;
DECLARE cursor_i CURSOR FOR SELECT COLUMN_NAME, TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA='xxxxx' AND TABLE_NAME='yyyyy' AND COLUMN_NAME = 'zzzzz';
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;
OPEN cursor_i;
read_loop: LOOP
FETCH cursor_i INTO cursor_COL, cursor_TAB;
SET tab := CONCAT('PD', '_', cursor_TAB, '_' , cursor_COL);
SET col1 := CONCAT(cursor_COL);
SET col2 := CONCAT(cursor_COL, '_', 'value');
IF done THEN
LEAVE read_loop;
END IF;
SET @dyn_sql := CONCAT('CREATE TABLE ',tab,' AS SELECT Codevalue as ',col1,', valueLabel as ',col2,' from valuesets14 where varName = "',cursor_COL,'" and TableName = "',cursor_TAB,'";');
PREPARE stmt_dyn_view FROM @dyn_sql;
#SELECT @dyn_sql;
EXECUTE stmt_dyn_view;
DEALLOCATE PREPARE stmt_dyn_view;
END LOOP;
CLOSE cursor_i;
END;
$$
DELIMITER ;