JPA 条件语句

目录

• JPA if && in语句示例
• JPA sql语句调试
  • COALESCE
  • IS NOT NULL

JPA if && in语句示例

示例：

//按照参数顺序填入sql
    @Query(value = "select count(1) from exam where class=?1 AND if(COALESCE(?2,NULL) IS NOT NULL, status in (?2), 1=1) AND score=?3", nativeQuery = true)
    int countByParam(int className, List<Integer> statusList, int score);

    //按照参数顺序填入sql
    @Query(value = "select count(1) from exam where class=:class AND if(COALESCE(:statusList,NULL) IS NOT NULL, status in (:statusList), 1=1) AND score=:score", nativeQuery = true)
    int countByParam(@Param("class") int className, @Param("statusList")List<Integer> statusList, @Param("score")int score);

• 需要注意的是，list参数statusList不可以为empty list。 如果statusList.size() == 0，则设置statusList=null。

• 语句说明：if(exp1, exp2, exp3) 表示 return exp1 ? exp2 : exp3。exp3一般是 1=1，一个空操作占位，使得sql语句合法。

• ?1 和 :class 是两种带入参数的方法，不可在同一个sql语句中出现，否则报错：Mixed parameter strategies - use just one of named, positional or JPA-ordinal strategy

JPA sql语句调试

application.properties 中添加配置

spring.jpa.show-sql=true # 显示sql语句
spring.jpa.properties.hibernate.format_sql=true #sql语句格式规范

关于上述if & in 语句的调试，看下check list empty的几种写法和问题

COALESCE

@Query(value = "select count(1) from exam where if(COALESCE(:statusList,NULL) IS NOT NULL, status in (:statusList), 1=1) AND score=:score", nativeQuery = true)
int countByParam(@Param("statusList")List<Integer> statusList, @Param("score")int score);

• statusList = [1]

    select
        count(1) 
    from
        exam 
    where
        if(COALESCE(?,NULL) IS NOT NULL, status in (?), 1=1) 
        and score=? 

• statusList = [1,2]

    select
        count(1)  
    from
        exam 
    where
        if(COALESCE(?, ?,NULL) IS NOT NULL, status in (?, ?), 1=1) 
        and score=? 

• statusList=[]

    select
        count(1)  
    from
        exam  
    where
        if(COALESCE(,NULL) IS NOT NULL, status in (), 1=1) 
        and score=? 

sql语句中有空白，会报错 You have an error in your SQL syntax,...

• statusList = null

    select
        count(1)  
    from
        exam  
    where
        if(COALESCE(?,NULL) IS NOT NULL, status in (?), 1=1) 
        and score=? 

IS NOT NULL

@Query(value = "select count(1) from exam where if(:statusList IS NOT NULL, status in (:statusList), 1=1) AND score=:score", nativeQuery = true)
int countByParam(@Param("statusList")List<Integer> statusList, @Param("score")int score);

• statusList = [1]

    select
        count(1)  
    from
        exam  
    where
        if(? IS NOT NULL, status in (?), 1=1) 
        and score=? 

• statusList = [1,2]

    select
        count(1)  
    from
        exam  
    where
        if(?, ? IS NOT NULL, status in (?, ?), 1=1)  
        and score=? 

sql语句有误，报错：You have an error in your SQL syntax

• statusList = []

    select
        count(1)  
    from
        exam  
    where
        if( IS NOT NULL, status in (), 1=1)   
        and score=? 

sql语句有误，报错：You have an error in your SQL syntax

• statusList = null

    select
        count(1)  
    from
        exam  
    where
        if(? IS NOT NULL, status in (?), 1=1)   
        and score=? 

where 子句实际为 where 1=1 and score=?

参考：
官方文档