【YashanDB知识库】MySQL的FIND_IN_SET如何在YashanDB改写

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前言

MySQL应用使用的SQL的Where条件存在FIND\_IN\_SET，无法在YashanDB直接执行，需要改写。本文探讨不兼容的原因，并给出改写手段。

问题

SQL示例

MySQL执行成功

mysql> select c1 from t1 where find_in_set(c2,'a,b,c'); +------+ | c1 | +------+ | 1 | +------+ 1 row in set (0.00 sec)

YashanDB报错

SQL> select c1 from t1 where find_in_set(c2,'a,b,c'); [1:25]YAS-04336 boolean expression expected

原因 MySQL的Boolean类型实际上是tinyint类型的同义词，0值为false，非0值为true。这意味着在MySQL的数值类型可以条件运算 参考：https://dev.mysql.com/doc/refman/8.4/en/numeric-type-syntax.html

mysql> select find_in_set('b','a,b,c') from dual; +--------------------------+ | find_in_set('b','a,b,c') | +--------------------------+ | 2 | +--------------------------+ 1 row in set (0.00 sec)   mysql> select find_in_set('d','a,b,c') from dual; +--------------------------+ | find_in_set('d','a,b,c') | +--------------------------+ | 0 | +--------------------------+ 1 row in set (0.00 sec)   mysql> select 1 from dual where 2; +---+ | 1 | +---+ | 1 | +---+ 1 row in set (0.00 sec)   mysql> select 1 from dual where 0; Empty set (0.00 sec)

但是，YashanDB的tinyint类型不能参与条件运算

SQL> select find_in_set('b','a,b,c') from dual; FIND_IN_SET('B','A,B --------------------                    2   1 row fetched. SQL> select find_in_set('d','a,b,c') from dual; FIND_IN_SET('D','A,B --------------------                    0   1 row fetched. SQL> select 1 from dual where 2; [1:26]YAS-04336 boolean expression expected SQL> select 1 from dual where 0; [1:26]YAS-04336 boolean expression expected

改写方案 按照find\_in\_set的逻辑，可以对所有参与where条件的find\_in\_set进行文本替换，例如示例中的替换规则就是 where find\_in\_set( 替换 where 0 < find\_in\_set(

SQL> select c1 from t1 where 0 < find_in_set(c2,'a,b,c');           C1 ------------            1 1 row fetched.

备注：一般而言，单个项目的源代码由于开发人员的习惯，对find\_in\_set的写法基本类似，所以往往可以用少数文本替换规则，就能对所有不兼容的find\_in\_set进行改写