该表已存在于新的SQL Server数据库中

Question

I'm writing a script to create a bunch of tables in SQL Server. As I write the script, I want to create and delete the database. The problem is that the I get an error saying that the object already exists.

Here is my example script

DECLARE @db_name varchar(20);
DECLARE @command varchar(100);
SET @db_name='testdb';

SET @command='DROP DATABASE ' + @db_name
IF EXISTS(SELECT * FROM sys.databases WHERE name=@db_name)
    exec(@command)

SET @command='CREATE DATABASE ' + @db_name
EXEC(@command)

--listing databaes
SELECT name from master.dbo.sysdatabases
-- using our database
SET @command='USE ' + @db_name
EXEC(@command)

PRINT 'listing tables'
SET @command = 'SELECT table_name FROM ' + @db_name + '.INFORMATION_SCHEMA.TABLES WHERE table_type = "base TABLE"'
EXEC(@command)
CREATE TABLE stuff(
    name VARCHAR(30) PRIMARY KEY NOT NULL,
    weight INT,
    quantity INT)

and the output I get is

name                                                                                                                            
------------    
master                                                                                                                          
tempdb                                                                                                                          
model                                                                                                                           
msdb                                                                                                                            
testdb                                                                                                                          
SW 

(6 rows affected)
listing tables
table_name                                                                                                                      

Error:

Msg 2714, Level 16, State 6, Server Orange, Line 22
There is already an object named 'stuff' in the database.

I run this on a Linux mint machine, a freshly installed SQL Server, and I use sqlcmd . I guess I can put a drop/delete command before the creating the table, but this shouldn't happen to begin with. What is going on here?

Answer 1

When you execute a USE statement from dynamic SQL, the database context reverts back to the original database context (master?) when the executed batch completes. You'll need to add a USE to the CREATE TABLE script and execute it using dynamic SQL too:

SET @command = N'USE' + QUOTENAME(@db_name) + N';
CREATE TABLE stuff(
    name VARCHAR(30) PRIMARY KEY NOT NULL,
    weight INT,
    quantity INT);
';

Answer 2

bind the create table statement inside a object existence check. like this

IF OBJECT_ID('stuff') IS NULL
BEGIN

CREATE TABLE stuff(
    name VARCHAR(30) PRIMARY KEY--NOT NULL is not needed as the primary key does not allow NULL,
    weight INT,
    quantity INT)

END