Question

我在“IF”附近遇到语法错误，并带有以下查询：

myDataBase.execSQL("IF EXISTS (SELECT * FROM ANSWERS WHERE QUESTION_ID=" + id +" AND PLAYER ='" + player + "')" +
                "UPDATE ANSWERS SET "+field+"=1"
                + " WHERE QUESTION_ID=" + id + " AND LEVEL =" + level +" AND PLAYER='" + player + "' ELSE "
                + "INSERT INTO ANSWERS (level, player, question_id, "+field+") VALUES (level, player, id, 1)");

不知道我哪里出错了..有人看到了吗？

 near "IF": syntax error: IF EXISTS (SELECT * FROM ANSWERS WHERE QUESTION_ID=6 AND PLAYER ='nob')UPDATE ANSWERS SET showhint1=1 WHERE QUESTION_ID=6 AND LEVEL =1 AND PLAYER='nob' ELSE INSERT INTO ANSWERS (level, player, question_id, showhint1) VALUES (level, player, id, 1)

Answer 1

请参阅this question的答案：

select exists(
    select * from answers ...
);

Answer 2

编辑：我喜欢这条评论的原始答案：sackoverflow.com/questions/418898 / ... - zapl 7分钟前。我不知道你能做到这一点。它的效率非常高......

我做得很快。希望你能得到这个想法...所以这些变量和东西将在非sql代码中。我建议使用存储过程或类似的东西，如果你可以....或完全分离所有部分（看它是否存在，基于这个sql，或如果它不做这个sql）。

仅使用更新语句....如果表中不存在变量，则不会更新任何内容。并且只使用insert语句...如果表中存在变量，则不会插入任何内容。除了这两个陈述之外，不需要做出if或者任何事情来实际检查以确定答案中是否存在某些内容。

create table #answers (question_id int, player int, level int, other_field int) 

insert into #answers values (1,1,1,1) 
insert into #answers values (2,1,1,1)  


declare @question_id int
declare @player int
declare @level int
declare @other_field int

set @question_id=1
set @player=1 
set @level=1
set @other_field=1

-- if it exists already 
update a
    set     other_field=@other_field  
    from    #answers as a
    where   QUESTION_ID=@question_id and 
            PLAYER=@player and 
            other_field<>@other_field 



set @question_id=4
set @player=4
set @level=1
set @other_field=1


-- if it doesn't exist
insert into #answers (question_id, player, level, other_field)
        select  x.QUESTION_ID, x.player, @level, @other_field
        from    #answers a 
                right outer join 
                    (select @question_id as QUESTION_ID,
                            @player as player) as x 
                    on x.QUESTION_ID=a.QUESTION_ID and 
                        x.player=a.player
        where   a.player is null and a.question_id is null

或者如果它不存在（更麻烦但更短）

-- if it doesn't exist
insert into #answers (question_id, player, level, other_field)
        select  distinct  @QUESTION_ID, @player, @level, @other_field  
        from    #answers 
        where   not exists (select 1 from #answers where 
                                QUESTION_ID=@question_id and 
                                    PLAYER=@player )

Answer 3

If exists不是在SQL更新语句中使用的有效关键字。

如果存在查询，则“IF”附近出错

3 个答案: