如果通过执行动态 SQL 命令在 table 中可用列，则当 select 列为 return 值时列名不明确

Question

如果列在table中可用，我想return一个列值，如果没有，return一个默认值，那么当我遇到COLUMN_NAME模棱两可的错误时加入两个 table SHAIN1 和 RIREKI14。如果 select 来自一个 table，那么查询工作正常，但如果我加入两个 table，我就会遇到问题。

declare @sql nvarchar(max) = ' SELECT 1 as id, '+ (case when exists (SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA ='dbo' and TABLE_NAME='RIREKI14' and COLUMN_NAME='KOM001') then 'KOM001' else 'NULL' end) + ' as day ' + ' From RIREKI14 join SHAIN1 on RIREKI14.INCODE = SHAIN1.INCODE  '; exec sp_executesql @sql

请帮帮我！

Answer 1

这是你的逻辑：

declare @sql nvarchar(max) = '
SELECT 1 as id, '+
    (case when exists (SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA  = 'dbo' and TABLE_NAME = 'RIREKI14' and COLUMN_NAME = 'KOM001')
          then 'KOM001'
          else 'NULL'
     end) + ' as day ' + '
From RIREKI14 join
     SHAIN1
     on RIREKI14.INCODE = SHAIN1.INCODE
';

exec sp_executesql @sql;

唯一可能出现歧义的列名是来自 case 的名称。那么，让我们限定一下：

declare @sql nvarchar(max) = '
SELECT 1 as id, '+
    (case when exists (SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA  = 'dbo' and TABLE_NAME = 'RIREKI14' and COLUMN_NAME = 'KOM001')
          then 'r.KOM001'
          else 'NULL'
     end) + ' as day ' + '
From RIREKI14 r join
     SHAIN1 s
     on r.INCODE = s.INCODE
';

exec sp_executesql @sql;

如果通过执行动态 SQL 命令在 table 中可用列，则当 select 列为 return 值时列名不明确

Ambiguous column name when select a column to return value if column is available in table by Execute Dynamic SQL commands

sql

sql-server

dynamic-sql

information-schema

ambiguous-call