JPA 條件語句

目錄

• JPA if && in語句示例
• JPA sql語句調試
  • COALESCE
  • IS NOT NULL

JPA if && in語句示例

示例：

//按照參數順序填入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);

    //按照參數順序填入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參數statusList不可以為empty list。 如果statusList.size() == 0，則設置statusList=null。

• 語句說明：if(exp1, exp2, exp3) 表示 return exp1 ? exp2 : exp3。exp3一般是 1=1，一個空操作占位，使得sql語句合法。

• ?1 和 :class 是兩種帶入參數的方法，不可在同一個sql語句中出現，否則報錯：Mixed parameter strategies - use just one of named, positional or JPA-ordinal strategy

JPA sql語句調試

application.properties 中添加配置

spring.jpa.show-sql=true # 顯示sql語句
spring.jpa.properties.hibernate.format_sql=true #sql語句格式規范

關於上述if & in 語句的調試，看下check list empty的幾種寫法和問題

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語句中有空白，會報錯 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語句有誤，報錯：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語句有誤，報錯：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 子句實際為 where 1=1 and score=?

參考：
官方文檔