SQL Server Learning Notes (Fri)--Query

Basic syntax structure for queries:

Select Column name/* from table name [where restriction] [order by order]

1. Query all rows and columns:

SELECT * FROM table name

2, Query department branches and columns: (Some columns use commas, to limit, some lines use where conditions to limit)

Select Column Name 1, column name 2 from table name where restriction condition

3. Use the alias of the column in the query:

Use as, use = (assign values from right to left), use spaces

4. Query null value is NULL

5, Sort: ASC Ascending, desc descending

Example:

Select  from where username like ' li% '-- selects all users in the UserInfo table username with Lee start Selectfromwhere payway<> ' Online Banking '--select userinfo form Payway payment method is not equal to "online banking" userid, Usern, payway three columns

userid as User ID, username =username, phone call from UserInfo where username like ' Zhang% '
--Using aliases

SELECT * from userinfo where email is null
--Using IS null

Email is null or email= '
--is null: Never entered data
--": entered data, then deleted

SQL Server Learning Notes (Fri)--Query