PHP operation MySQL

Internal connection

Syntax rules: Select *| Field List from the left table inner join right table on the left table. field = Right table. field;

External connection

1. Left Outer connection:
Syntax rules: The Select *| field list from the left table and the right table on the left outer join. field = Right table. field;

2. Right outer connection:
Syntax rules: The Select *| field list from the left table right outer join to the left table. field = Right table. field;

Natural connection

1. Natural Inner Connection
Syntax: Left table natural INNER join right table

2. Natural outer Connection
Syntax: Left table natural left|right join right Table

Sub-query (scalar quantum query)

Scalar Quantum query: Select field List (function) from data table;

Column query: That is, to return a single row of subqueries
Syntax: Select field from data table;

Row subquery: Returns a row of subqueries.
Grammatical form:
Select *| field list from table name where (field 1, Field 2 ...). ) = (Row subquery result)

Table subquery: Select *| Field List from sub-query result as alias WHERE clause ...

Exists sub-query
Exists is primarily used to make judgments, and the return result is a Boolean value!
Application Scenarios:
Registered users, you must ensure that the user name is not registered, at this time you can first query the user's user name exists!

Syntax form: SELECT EXISTS (SELECT * from table name where ...)

PHP operation MySQL
First step: Establish connection authentication
$link = mysql_connect ("localhost:3306", "root", "password");
Step Two: send operation instructions
$sql = "Set names UTF8";
$result = mysql_query ($sql);
Step three: Return processing results
Var_dump ($result);
Fourth step: Disconnecting
Mysql_close ($link);

PHP Extract Resource result set
PHP Extract Resource result sets are basically implemented using the Mysql_fetch series functions!
The syntax form is: mysql_fetch_array (resource result set)

Error debugging function

Mysql_errno (): Get the wrong number!
Mysql_error (): Get the wrong information!

Encapsulating database Connection files

PHP implementation and additions to the search

Insert Data function: mysql_insert_id ()

Delete and update data
Use function: Mysql_affected_rows ()

PHP operation MySQL