We are able to connect to MSSQL Server Management Studio with Windows Authentication but unable to connect with SQL Server Authentication. The 'sa' login details are correct but still getting the following error message:
Login failed for user 'sa'. (Microsoft SQL Server, Error: 18456)
In order to resolve the issue, please refer to the following steps:
1. Login to the MSSQL Server Management Studio with Windows Authentication.
2. In SQL Server Management Studio Object Explorer, right-click the server, and then click Properties.
3. Under the Server Properties, select a page of "Security".
4. Select the Server authentication as "SQL Server and Windows Authentication mode" and click Ok.
.
5. Restart the SQL Services and then try to login with 'sa' details.
Copy from：http://forums.eukhost.com/f15/login-failed-user-sa-microsoft-sql-server-error-18456-a-12544/
我按照這樣操作，sa登陸成功了。其實這不是什么技術方面的問題，但是sql本來自身的配置不常操作，如果沒有什么經驗的話，遇到這種問題也是比較麻煩。
出現這中問題其實就是ssms客戶端程序配置的問題，裝完數據庫后，默認的設置是禁用 SQL Server Authentication 即SQL Server身份認證，只啟用Windows認證模式。
希望你遇到這樣的問題的時候，可以看到這篇轉載的文章!