我喜欢@Eduardo的回答，我也喜欢公认的答案。我喜欢从这样的东西中得到一个布尔值，所以我把它写出来了。

CREATE FUNCTION dbo.DatabaseExists(@dbname nvarchar(128))
RETURNS bit
AS
BEGIN
    declare @result bit = 0 
    SELECT @result = CAST(
        CASE WHEN db_id(@dbname) is not null THEN 1 
        ELSE 0 
        END 
    AS BIT)
    return @result
END
GO

现在你可以这样使用它:

select [dbo].[DatabaseExists]('master') --returns 1
select [dbo].[DatabaseExists]('slave') --returns 0

  Public Function SQLDatabaseExist(ByVal DefaultConnectionString As String, ByVal DataBaseName As String) As Boolean
Try
    'CREATE DATABASE
    Dim SqlString As String = ""
    SqlString = "SELECT CASE WHEN EXISTS (SELECT name FROM master.dbo.sysdatabases WHERE name = N'" & DataBaseName & "') THEN CAST (1 AS BIT) ELSE CAST (0 AS BIT) END"
    Dim ExcRet As Integer = 0
    Using connection As New SqlConnection(DefaultConnectionString)
        Dim command As New SqlCommand(SqlString, connection)
        command.Connection.Open()
        ExcRet = command.ExecuteScalar()
        command.Connection.Close()
        command.Dispose()
    End Using
    Return ExcRet
Catch ex As Exception
    Return False
End Try

结束函数

注意连接字符串中的初始目录必须是master! '示例默认连接字符串

Dim DefaultConnectionString As String = "Data Source=localhost\SQLSERVER2008;Initial Catalog=Master; User ID=SA; Password='123123'; MultipleActiveResultSets=false; Connect Timeout=15;Encrypt=False;Packet Size=4096;"

试试这个

IF EXISTS 
   (
     SELECT name FROM master.dbo.sysdatabases 
    WHERE name = N'New_Database'
    )
BEGIN
    SELECT 'Database Name already Exist' AS Message
END
ELSE
BEGIN
    CREATE DATABASE [New_Database]
    SELECT 'New Database is Created'
END

实际上，最好使用:

IF DB_ID('dms') IS NOT NULL
   --code mine :)
   print 'db exists'

请参阅https://learn.microsoft.com/en-us/sql/t-sql/functions/db-id-transact-sql并注意，这对于Azure SQL数据库是没有意义的。

IF EXISTS (SELECT name FROM master.sys.databases WHERE name = N'YourDatabaseName')
  Do your thing...

顺便说一下，这直接来自SQL Server Studio，所以如果你有这个工具，我建议你开始使用各种可用的“Script xxxx AS”函数。会让你的生活更轻松!：）

来自微软的脚本:

DECLARE @dbname nvarchar(128)
SET @dbname = N'Senna'

IF (EXISTS (SELECT name 
FROM master.dbo.databases 
WHERE ('[' + name + ']' = @dbname 
OR name = @dbname)))