问题描述
我列出了需要从 SQL Server 中删除的表(大约 100++).以下是我将使用的示例代码
I've list of tables (around 100++) that need to be dropped from SQL Server. Below is the sample code that I would use
IF OBJECT_ID('dbo.DS_Area_TBL', 'U') IS NOT NULL drop table dbo.DS_Area_TBL Print 'dbo.DS_Area_TBL has been dropped'
我需要用其他表名替换表名 100++ 时间.如何编写一个可以自动生成查询列表的动态sql脚本?
I need to replace table name 100++ time with other table name. How to write a dynamic sql script that can auto generate list of queries?
推荐答案
你可以先生成脚本然后用动态 sql 执行:
You could first generate script then execute with dynamic sql:
CREATE TABLE a(a INT); CREATE TABLE b(a INT); CREATE TABLE c(a INT); CREATE TABLE d(a INT); CREATE TABLE e(a INT); CREATE TABLE tab(tab_name SYSNAME); -- here are table names stored INSERT INTO tab VALUES ('a'),('b'),('c'),('d'),('e'); -- main part DECLARE @sql NVARCHAR(MAX); SELECT @sql = STUFF((SELECT ' ' + FORMATMESSAGE( 'IF OBJECT_ID(''%s'', ''U'') IS NOT NULL BEGIN DROP TABLE %s; PRINT ''%s has been dropped ''; END ', QUOTENAME(tab_name),QUOTENAME(tab_name),QUOTENAME(tab_name)) FROM tab FOR XML PATH('')), 1, 1, ''); PRINT @sql; -- for debug EXEC [dbo].[sp_executesql] @sql;
如果你使用的SQL Server版本低于2012你需要用字符串连接+来改变FORMATMESSAGE.
If you use version of SQL Server lower than 2012 you need to change FORMATMESSAGE with string concatenation +.
您可以通过修改模板轻松地使用自定义架构等扩展此脚本:
You could easily extend this script with custom schema and so on by modifying template:
'IF OBJECT_ID(''%s'', ''U'') IS NOT NULL BEGIN DROP TABLE %s; PRINT ''%s has been dropped ''; END '
输出:
IF OBJECT_ID('[a]', 'U') IS NOT NULL BEGIN DROP TABLE [a]; PRINT '[a] has been dropped '; END IF OBJECT_ID('[b]', 'U') IS NOT NULL BEGIN DROP TABLE [b]; PRINT '[b] has been dropped '; END IF OBJECT_ID('[c]', 'U') IS NOT NULL BEGIN DROP TABLE [c]; PRINT '[c] has been dropped '; END IF OBJECT_ID('[d]', 'U') IS NOT NULL BEGIN DROP TABLE [d]; PRINT '[d] has been dropped '; END IF OBJECT_ID('[e]', 'U') IS NOT NULL BEGIN DROP TABLE [e]; PRINT '[e] has been dropped '; END
工作原理:
- XML + STUFFfor string concatenation 是 SQL Server 的常用习惯用法,类似于 MySQL 中的 GROUP_CONCAT.您可以将其视为一种将多个 IF BEGIN END 块组合成一个字符串的方法.
- FORMATMESSAGE 将替换 %s 带有实际表名(引用以避免 SQL 注入攻击)
- PRINT 用于调试以检查生成的查询,可以注释
- sp_executesql 将执行 SQL 字符串
- XML + STUFF for string concatenation is common idiom with SQL Server, works like GROUP_CONCAT in MySQL. You can think about it as a way to combine multiple IF BEGIN END chunks into one string.
- FORMATMESSAGE will replace %s with actual table names(quoted to avoid SQL Injection attacks)
- PRINT is for debug to check generated query, can be commented
- sp_executesql will execute SQL string