生成drop table语句列表的动态sql脚本

2021-09-10 00:00:00 sql tsql sql-server

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:

  1. 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.
  2. FORMATMESSAGE 将替换 %s 带有实际表名(引用以避免 SQL 注入攻击)
  3. PRINT 用于调试以检查生成的查询，可以注释
  4. sp_executesql 将执行 SQL 字符串
  1. 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.
  2. FORMATMESSAGE will replace %s with actual table names(quoted to avoid SQL Injection attacks)
  3. PRINT is for debug to check generated query, can be commented
  4. sp_executesql will execute SQL string

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