Sql 简化If和elseif查询

这里我检查三个表上的条件，如果三个表中存在一列，它应该打印“1”，如果它只存在于第一个表和第三个表中，则打印“1 0 1”。像这样，我写了8条条件语句。但是我想要对上述存储过程进行简化查询

我想对上面的示例进行最简单的查询-我如何才能做到这一点？

试试这个：

ALTER PROCEDURE spDisplayTableNames1
    @T_ID INT OUT,
    @BatchNumber VARCHAR(30) OUT
AS
BEGIN
    IF((SELECT COUNT(*) FROM tblPacks 
        WHERE T_ID = @T_ID 
          AND BatchNumber = @BatchNumber) = 0) 
    AND ((SELECT COUNT(*) FROM tblBlisters 
          WHERE T_ID = @T_ID 
            AND BatchNumber = @BatchNumber) = 0) 
    AND ((SELECT COUNT(*) FROM tblShippers 
          WHERE T_ID = @T_ID AND BatchNumber = @BatchNumber) = 0)
BEGIN 
    PRINT '0 0 0'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0)
BEGIN
Print '1 0 0'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0)
BEGIN
Print '0 1 0'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0)
BEGIN
Print '0 0 1'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0)
BEGIN
Print '1 1 0'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0)
BEGIN
Print '1 0 1'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0)
BEGIN
Print '0 1 1'
END
ELSE IF((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0) AND ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)>0)
BEGIN
Print '1 1 1'
END

END

试试这个

declare @prt varchar(10);
if ((SELECT COUNT(*) FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0)
    set @prt = '0';
else
    set @prt = '1';

if ((SELECT COUNT(*) FROM tblBlisters WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0)
    set @prt = @prt + ' 0';
else
    set @prt = @prt + ' 1';

if ((SELECT COUNT(*) FROM tblShippers WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber)=0) 
    set @prt = @prt + ' 0';
else
    set @prt = @prt + ' 1'; 

print @prt;

如果记录存在于表中，则

计数（不同的1）

将给出一个

1

，否则为零（

0

）

---

接下来，通过将每个记录追加到变量中，将结果集存储在变量中。

我之所以回答这个问题，是因为

if（select count（*）…）

是一个非常糟糕的习惯用法。这需要运行聚合查询以查看是否存在单行。更好的方法是

if exists（）

此外，所有条件逻辑都可以在

选择中完成：

DECLARE @PRINT VARCHAR(10)=''

SELECT @PRINT = @PRINT+CAST(PR AS VARCHAR(10))+' ' FROM (
SELECT COUNT(DISTINCT 1) AS PR FROM tblPacks WHERE T_ID=@T_ID AND BatchNumber=@BatchNumber
UNION ALL
SELECT COUNT(DISTINCT 1) FROM tblBlisters WHERE  T_ID=@T_ID AND BatchNumber=@BatchNumber
UNION ALL
SELECT COUNT(DISTINCT 1) FROM tblShippers WHERE  T_ID=@T_ID AND BatchNumber=@BatchNumber
)A

SELECT @PRINT

我认为这会在开始时提供额外的空间，例如“1 0 0”而不是“1 0 0”。但这很容易解决…不。它不会将空格作为前缀。但空间将在最后到来。如果我们需要，我们可以移除。但是尾随空格不重要你是对的，这是尾随空格，我误读了代码。可以通过LTRIM（）或RTRIM（）轻松修复这两者之一。。。
declare @prt varchar(10);

select @prt = (case when exists (select 1 from tblpacks where T_ID = @T_ID  and BatchNumber = @BatchNumber)
                    then '0' else '1'
               end) +
              (case when exists (select 1 from tblBlisters where T_ID = @T_ID and BatchNumber = @BatchNumber)
                    then ' 0'
                    else ' 1'
               end) +
              (case when exists (select 1 from tblShippers where T_ID = @T_ID and BatchNumber = @BatchNumber)
                    then ' 0';
                    else ' 1'
               end)
              )
print @prt;