The most commonly used SQL command is SELECT statement. SQL SELECT statement is used to query or retrieve data from a table in the database. A query may retrieve information from specified columns or from all of
Capabilities of theSELECTStatement(SELECT语句的功能) Data retrieval from data base is done through appropriate and efficient use of SQL. Three concepts from relational theory encompass the capability of the SELECT statement: projection, selection, and joining. Projection(投影): A project operation sele...
The syntax of an SQL SELECT statement is mostly the same between different database vendors (Oracle, SQL Server, MySQL, PostgreSQL): SELECT[ALL|DISTINCT]{ select_list }[INTOnew_table]FROM{ table_source }[WHEREsearch_condition][GROUPBYgroup_expression][HAVINGsearch_condition][ORDERBYorder_clause]...
Just remember that the select statement is made up of two main parts: the SELECT SELECT and the FROM portion. In general, the database first looks to see if these keywords are present, and if they are not it triggers a Syntax error. This is just a fancy phrase for “you have misspel...
TheSELECTstatement is used to select data from a database. ExampleGet your own SQL Server Return data from the Customers table: SELECTCustomerName, CityFROMCustomers; Try it Yourself » Syntax SELECTcolumn1,column2, ... FROMtable_name; ...
The SELECT clause is used to retrieve information from database table(s). Let's have a look at a very simple SQL SELECT statement selecting data from a database table called Cars, as this is the easiest way to understand how it works. ...
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> 新建userdb库,切换到userdb库: mysql> CREATE DATABASE userdb; Query OK, 1 row affected (0.00 sec) mysql> USE userdb; Database changed 新建userlist表,字段设置及相关操作参考如下: ...
SELECT last_name, department_id FROM employees Oracle Databaseでは、完全なSQL文のみが実行されます。次のような不完全文を実行しようとすると、テキストの不足を示すエラーが発生します。 SELECT last_name; Oracle SQL文は、次のカテゴリに分類されます。
SELECT * INTO CustomersBackup2017 FROM Customers; The following SQL statement uses the IN clause to copy the table into a new table in another database:SELECT * INTO CustomersBackup2017 IN 'Backup.mdb' FROM Customers; The following SQL statement copies only a few columns into a new table:...
数据操纵语言(Data Manipulation Language, DML)是用于数据库操作,对数据库其中的对象和数据运行访问工作的编程语句。 DML 的主要功能是访问数据,因此其语法都是以读写数据库为主。 DML 的核心指令是 INSERT、UPDATE、DELETE、SELECT。这四个指令合称 CRUD(Create, Read, Update, De...