SQL (Struct Query Language) Structured Query language is a standard language for relational database management systems. Create, SELECT, INSERT, UPDATE, DELETE, DROP TABLE.
1, SELECT
SELECT [Column1, Column2, etc] from tablename [where condition];
E.g:
Select Select Firstname, Lastname, City from Employee Where Firstname Like E%;
Select * from Employee where firstname = 'ma';
2, CREATE
Create Table Tablename (Column1 Data Type, Column2 Data Type, Column3 Data Type);
Create Table Tablename (Column1 Data Type [Constraint], Column2 Data Type [Constraint], Column3 Data Type [Constraint]);
For example: Create Table Employee (Firstname Varchar (15), Lastname Varchar (20), Age Number (3), Address Varchar (30), City Varchar (20));
3, INSERT
INSERT INTO TABLENAME (First_Column, ... Last_Column) Values (first_value, ... last_value);
For example: INSERT INTO Employee (FirstName, Lastname, Age, Address, City) Values ('li', 'ming', '45', 'No.77 Changan Road', 'beijing');
4, Update
Update Tablename Set ColumnName = NewValue [, NextColumn = newValue2 ...] Where columnName Operator value [and or column operator value];
For example: Update Employee Set Age = age 1 where first_name = 'mary'and last_name =' Williams';
5, Delete
Delete from tablename where columnName Operator value [and or column operator value];
For example: delete from Employee Where LastName = May;
6, Drop Table
Drop Table TableName;
For example: DROP TABLE EMPLOYEE
Select ... from detailed usage must be
DistinctsumavgcountGroup byhavingalias
