Question

我只是设置一个SQL存储过程以按特定顺序返回特定行（从更多到不太重要）：

-- 1st Level -> Query a more detailed object...
SELECT ... WHERE something
-- if a result is find, the SP is returning the correct row.
-- if rowcount = 0 then, the SP is returning an empty row 
-- and continues with the next query (less specific than the 1st one).

IF @@ROWCOUNT = 0
BEGIN
SELECT .... WHERE something else... 
 -- Again, if a result exists, the SP returns the correct row, but also 
 -- the result of the 1st query is returned without rows...
 IF @@ROWCOUNT = 0
 BEGIN
 SELECT .... WHERE something else again...
 END
END

是否有任何选项只返回返回非空行的SELECT语句？我不想返回空行...并且每次该行是第一个查询的“子级别”时，我在正确的行之前得到空结果。

我正在考虑创建一个表变量。有没有更好的方法？

Answer 1

由于您正在寻找缺少行的原因，为什么不在您的过程中使用if / else语句。类似的东西：

If exists(/*firstQuery*/ SELECT ... WHERE something) begin
   SELECT ... WHERE something
end else if exists (/*secondQuery*/ SELECT .... WHERE something else... ) begin
   SELECT .... WHERE something else... 
end else /*Third query*/ begin
    SELECT .... WHERE something else again...
end

请记住，当检查存在某些内容时，您应该只选择一列（例如id），就像计算了列一样，这样会减慢您的过程。

存储过程仅返回SELECT行

1 个答案: