如果语句符合SQL，则选择特定项

Question

存在类似的内容：

@isParamSet int
SELECT
CASE
WHEN @isParamSet=1 THEN Name, Surname
END
telNumber
FROM DETAILS

这当然是一个存储过程。

Answer 1

如果SQL Server：

IF @isParamSet = 1
  SELECT
    Name,
    Surname,
    telNumber
  FROM DETAILS
ELSE
  SELECT
    telNumber
  FROM DETAILS

您还可以使用Dynamic-SQL构建列列表。

DECLARE @sql NVARCHAR(MAX) = 
      N'SELECT
        {other}
        telNumber
      FROM DETAILS';

SELECT @sql = REPLACE(@sql, '{other}', CASE
                                       WHEN @isParamSet = 1 THEN 'Name, Surname, '
                                       ELSE ''
                                       END );

EXEC [dbo].[sp_executesql]
     @sql;

修改

您可以将参数传递给Dynamic-SQL，如

DECLARE @sql NVARCHAR(MAX) = 
      N'SELECT
        {other}
        telNumber
      FROM DETAILS
      WHERE country = @country';

SELECT @sql = REPLACE(@sql, '{other}', CASE
                                       WHEN @isParamSet = 1 THEN 'Name, Surname, '
                                       ELSE ''
                                       END );

EXEC [dbo].[sp_executesql]
     @sql
     ,N'@country NVARCHAR(100)' -- pass correct type
     ,@country;

Answer 2

试试这个

declare @sql nvarchar(max)

set @sql  = 'SELECT ' +
CASE
WHEN @isParamSet=1 THEN 'Name, Surname,' else ''
END + '
telNumber
FROM DETAILS'

Exec sp_executesql @sql