A. SQL tutorial
1. SQL syntax
Dml
Select query data
Update updates data
Delete Deletes data
INSERT INTO Inserts data
Ddl
Create DATABASE table
ALTER DATABASE modifies databases
CREATE table Creating tables
ALTER TABLE Modify tables
drop TABLE Delete Tables
CREATE index
Drop INDEX to delete indexes
Set names UTF8; sets the charset used
The SQL statement is not case sensitive.
2. SQL SELECT
SELECT * FROM table name
Select Column name from table name
Select Lastname,firstname from persons;
3. SQL SELECT DISTINCT
SELECT DISTINCT column_name,column_name from table_name;
Select distinct country from websites;
4. SQL WHERE
Select Column_name,column_name from table_name where column_name operator value;
SELECT * FROM websites where country= ' cn '
SQL uses single quotation marks (') to surround text values
If the number field, do not use single quotation marks.
SELECT * FROM websites where id=1
The following operators can be used in a where statement:
= equals
<> does not equal (you can use! = in some versions of SQL)
> Greater than
< less than
>= greater than or equal to
<= less than or equal to
Between within a certain range
Like search for a pattern
In developing multiple possible values for a column
5. SQL ADN & OR
If both the first condition and the second condition are true, the AND operator displays a record.
If only one of the first and second conditions is true, the OR operator displays a record.
SELECT * FROM websites where country= ' cn ' and ALEXA>50
SELECT * from websites where country = ' USA ' or country= ' CN '
SELECT * from websites where Alexa > and (country= ' cn ' or country= ' USA ')
6. SQL ORDER by
The ORDER BY keyword is used to sort the result set by one column or multiple columns.
The order by keyword sorts records by default in ascending order. If you need to sort records in descending order, you can use the DESC keyword.
Select Column_name,column_name from table_name ORDER by Column_name,column_name Asc|desc
SELECT * FROM websites ORDER by Alexa
SELECT * FROM websites ORDER by Alexa Desc
SELECT * FROM websites ORDER by Country,alexa
7. SQL INSERT into
The INSERT INTO statement is used to insert a new record into the table.
INSERT INTO table_name values (V1,v2,v3,.....);
INSERT INTO table_name (C1,C2) values (V1,V2);
Insert INTO websites (name,url,alexa,country) VALUES (' Baidu ', ' https://www.baidu.com ', 4, ' CN ')
The ID column is automatically updated
Insert INTO websites (name,url,country) VALUES (' StackOverflow ', ' http:/stackoverflow.com ', ' ind ')
8. SQL UPDATE
UPDATE table_name Set c1 = V1,C2 = V2 where c3 = V3;
The WHERE clause specifies which record or records need to be updated. If you omit the WHERE clause, all the records will be updated!
Update websites set Alexa =5000,country= ' USA ' where name= ' rookie tutorial '
9. SQL DELETE
Delete FROM table_name where c1 = v1;
The WHERE clause specifies which record or records need to be deleted. If you omit the WHERE clause, all records will be deleted!
Delete from websites where name= ' Baidu ' and country = ' CN '
Delete all records
DELETE from TABLE_NAME;
Or
DELETE * FROM table_name;
This article is from "Zhongyong's personal blog" blog, make sure to keep this source http://zhuangyong.blog.51cto.com/12459964/1887175
First, personal summary of the Novice tutorial |sql tutorial Knowledge points (SQL Tutorial)