Question

如何实现以下查询 -

SELECT 
   CASE 
      WHEN COUNT(*) > 0 THEN 
         -- UPDATE operation
      ELSE 
         -- INSERT operation
   END AS [RESULT] 
FROM 
   [TABLE_1] 
WHERE 
   [CONDITION]

我正在使用SQL Server 2000。有人可以帮助我吗？

Answer 1

Use EXISTS not COUNT根据我的回答

IF EXISTS (SELECT * FROM [TABLE_1])
    UPDATE [TABLE_1] SET X = Y WHERE [CONDITION]
ELSE 
    INSERT INTO [TABLE_1] (X) VALUES (Y)

如果您期望更新比例很高，那么为什么要两次触摸表格呢？

UPDATE [TABLE_1] SET X = Y WHERE [CONDITION]
IF @@ROWCOUNT = 0 
    INSERT INTO [TABLE_1] (X) VALUES (Y)

对于SQL Server 2000上的很大比例的INSERT，你不能这样做：you need TRY/CATCH to handle duplicates根据我的回答

Answer 2

到目前为止，最简单的方法是使用两个单独的查询，例如：

IF (SELECT COUNT(*) FROM [TABLE_1]) > 0
    UPDATE [TABLE_1] SET X = Y WHERE [CONDITION]
ELSE 
    INSERT INTO [TABLE_1] (X) VALUES (Y)

根据选择的查询值执行查询

2 个答案: