sql可以有if else那种判断吗？

需要根据查询情况对数据进行插入
插入的数据是根据某个子查询的结果进行插入，可不可以有那种ifelse的sql，当子查询的结果多于一条的时候就不执行插入，
当子查询结果等于一条则将这个查询结果插入，如果没有就不进行插入？
这是插入的代码，如果通配符匹配到了多个纪录则插入失败，怎么解决这个问题呢?

INSERT INTO temp (quancheng, tyshxydm)
VALUES
    (
        (
            SELECT
                distname
            FROM
                municipaldepartmentslist
            WHERE
                DISTNAME LIKE 'fweFD%'
        ),
        (
            SELECT
                deptid
            FROM
                municipaldepartmentslist
            WHERE
                DISTNAME LIKE 'EFW%'
        )
    )

用case when 就可以实现if else。

一个case when 的实例：
SELECT t1.P_DATE,t1.AREA,IFNULL(t2.I_CODE,'M_INDEX0009') AS I_CODE,
case WHEN SumHour!=0 THEN ROUND((IFNULL(t2.M_E_CT,0))/((t1.SumHour)/10000),2) ELSE NULL END AS INDEX_VAL,
case WHEN SumHour1!=0 THEN ROUND((IFNULL(t2.MY_E_CT,0))/((t1.SumHour1)/10000),2) ELSE NULL END AS TB_INDEX_VAL,
case WHEN SumHour2!=0 THEN ROUND((IFNULL(t2.ML_E_CT,0))/((t1.SumHour2)/10000),2) ELSE NULL END AS HB_INDEX_VAL
FROM tmp_q_fixed_index_001 t1
LEFT JOIN
tmp_q_fixed_index_002 t2
ON
t1.P_DATE = t2.P_DATE AND t1.AREA=t2.AREA
WHERE t1.YXLX='1';

不知道你要达到什么效果，你的sql语句看起来很怪，正常来讲可以直接写：

INSERT INTO temp (quancheng, tyshxydm)
select distname,deptid  
FROM  municipaldepartmentslist
WHERE  +条件

如果非要这样处理的话，SqlServer可以这样处理，mysql的话应该差不多吧：

  if( (select COUNT( distname)FROM municipaldepartmentslist WHERE  DISTNAME LIKE 'fweFD%' )>1 
        or (select COUNT( deptid)FROM municipaldepartmentslist WHERE  DISTNAME LIKE 'EFW%' )>1  )  
  begin
    INSERT INTO temp (quancheng, tyshxydm)
    VALUES
        (
            (
                SELECT
                    distname
                FROM
                    municipaldepartmentslist
                WHERE
                    DISTNAME LIKE 'fweFD%'
            ),
            (
                SELECT
                    deptid
                FROM
                    municipaldepartmentslist
                WHERE
                    DISTNAME LIKE 'EFW%'
            )
        )

  end