First, Oracle retrieves data fromcustomerstable. Second, Oracle returns only values in thenamecolumn specified in theSELECTclause. Querying data from multiple columns# To query data from multiple columns, you s
Column renaming for function : Column Names « Select Query « Oracle PL / SQL Column renaming for function SQL> CREATE TABLE EMP( 2 EMPNO NUMBER(4) NOT NULL, 3 ENAME VARCHAR2(10), 4 JOB VARCHAR2(9), 5 MGR NUMBER(4), 6 HIREDATE DATE, 7 SAL NUMBER(7, 2), 8 COMM NUMBER(7...
column_3FROMtable_name;Code language:SQL (Structured Query Language)(sql) In this syntax, theDISTINCToperator uses the combination of values in thecolumn_1,column_2, andcolumn_3are evaluate the uniqueness of the data. Oracle allows you to useDISTINCTclause in theSELECTstatement only. Note that...
SQLite 支持 SELECT INTO 语法,但通常推荐使用 CREATE TABLE AS 语法来实现相同的功能。 语法: 1 2 CREATE TABLE new_table AS SELECT * FROM old_table; 特点: 同PostgreSQL 和 MySQL,SQLite 使用 CREATE TABLE AS 来创建新表并插入数据。 适用于轻量级的数据库和小规模数据操作。 5. Oracle Oracle 不直接...
可以指定一个或多个列进行分组。限制:支持使用LIMIT子句限制结果中的行数。可以指定要返回的最大行数。子查询:支持使用子查询来嵌套或关联多个查询。...以下是一个示例的SELECT子句的使用:SELECT column1, column2 * 2 AS column3, COUNT(*)FROM tableWHERE column1 > 10GROUP...
CREATE VIEW view_name AS SELECT column_names FROM table_name WHERE conditions; 事务和锁:保证数据安全 事务特点 1、事务的原子性 一组事务,要么成功;要么撤回。 2、稳定性 有非法数据(外键约束之类),事务撤回。 3、隔离性 事务独立运行。 一个事务处理后的结果,影响了其他事务,那么其他事务会撤回。
<with_query_name> [( <column_name> [, ...] )] AS ( <select> | <values> | <insert> | <update> | delete ) Copy where from_item can be one of: [ONLY] <table_name> [ * ] [ [ AS ] <alias> [ ( <column_alias> [, ...] ) ] ] ( <select> ) [ AS ] <alias> [(...
Oracle usage The Create Table As Select (CTAS) statement creates a new table based on an existing table. It copies the table DDL definitions (column names and column datatypes) and data to a new table. The new table is populated from the columns specified in theSELECTstatement, ...
Oracle usage The Create Table As Select (CTAS) statement creates a new table based on an existing table. It copies the table DDL definitions (column names and column datatypes) and data to a new table. The new table is populated from the columns specified in theSELECTstatement, or all colu...
[oracle@ef6d9de18e59 ~]$ sqlplus admin/admin123 SQL> CREATE TABLE PERSONS( ID NUMBER(10), NAME VARCHAR2(128) NOT NULL, PRIMARY KEY(ID) ); Table created. SQL> INSERT INTO "PERSONS" VALUES (1, 'zhangsan'); SQL> INSERT INTO "PERSONS" VALUES (2, 'lisi'); ...