SQL 两个表中的重复条件

Question

我是 SQL 的初学者，我很难摆脱重复的代码。我有一个条件 "AccountId=20"，我在 SQL 查询中使用了两次。 SQL 看起来像：

DELETE FROM Table_A WHERE FunctionId IN (Select FunctionId FROM Table_B WHERE AccountId=20);
DELETE FROM Table_B WHERE AccountId=20;

当我更改条件时，我必须更改代码中的两行。

我想清理重复的代码。我试过类似的东西：

DECLARE @condition datatypeForConditions = AccountId=20;
DELETE FROM Table_A WHERE FunctionId IN (Select FunctionId FROM Table_B WHERE @condition);
DELETE FROM Table_B WHERE @condition;

SQL 似乎没有条件数据类型，所以我不能声明这个变量。我什至可以为条件设置变量吗？我怎样才能避免在两个地方改变条件？

Answer 1

你可以这样实现

DECLARE @AccountId int;
@AccountID=20;
DELETE FROM Table_A WHERE FunctionId IN (Select FunctionId FROM Table_B WHERE AccountID=@AccountId);
DELETE FROM Table_B WHERE AccountID=@AccountId;

SQL 两个表中的重复条件

SQL Repeated Condition in Two Tables

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