MYSQL common functions in PHP (necessary for operating databases under PHP)

1. mysql_connect()-Establish a database connection
Format:
resource mysql_connect([string hostname [:port] [:/path/to/socket] [, string username] [, string password]])
Example:
$conn = @mysql_connect("localhost", "username", "password") or die("Cannot connect to Mysql Server");
Instructions: Use this connection Close the connection that must be displayed

2. mysql_pconnect()-Establish a database connection
Format:
resource mysql_pconnect([string hostname [:port] [:/path/to /socket] [, string username] [, string password]])
Example:
$conn = @mysql_pconnect("localhost", "username", "password") or dir("Cannot connect to Mysql Server ");
Note: Using this connection function does not require explicit closing of the connection. It is equivalent to using a connection pool

3. mysql_close()-Close the database connection
Example:
$conn = @mysql_connect("localhost", "username", "password") or die("Cannot connect to Mysql Server");
@mysql_select_db("MyDatabase") or die("Cannot Select this database, or the database does not exist");
echo "You have connected to the MyDatabase database";
mysql_close();

4. mysql_select_db()-Select database
Format:
boolean mysql_select_db(string db_name [, resource link_id])
Example:
$conn = @mysql_connect("localhost", "username", "password") or die(" Cannot connect to Mysql Server");
@mysql_select_db("MyDatabase") or die("This database cannot be selected, or the database does not exist");

5. mysql_query()-query MySQL
Format:
resource mysql_query (string query, [resource link_id])
Example:
$linkId = @mysql_connect("localhost", "username", "password") or die("Cannot connect to Mysql Server");
@mysql_select_db("MyDatabase") or die("Cannot select this database, or the database does not exist");
$query = "select * from MyTable";
$result = mysql_query($query);
mysql_close();
Explanation: If the SQL query is executed successfully, the resource identifier is returned, and FALSE is returned if it fails. If the update is executed successfully, TRUE is returned, otherwise FALSE is returned

6. mysql_db_query()-query MySQL
format:
resource mysql_db_query(string database, string query [, resource link_id])
Example:
$linkId = @mysql_connect("localhost", "username", "password") or die("Cannot connect to MysqlServer");
$query = "select * from MyTable";
$result = mysql_db_query("MyDatabase", $query);
mysql_close();
Note: In order to make the code clear, it is not recommended to use this function call

7. mysql_result()-Get and display data
Format:
mixed mysql_result (resource result_set, int row [, mixed field])
Example:
$query = "select id, name from MyTable order by name";
$result = mysql_query($query);
for($count=0;$count<=mysql_numrows($result);$count++)
{
$c_id = mysql_result($result, 0, "id");
$c_name = mysql_result($result, 0, "name");
echo $c_id,$c_name;
}
Description: The simplest and least efficient data acquisition function

8. mysql_fetch_row()-obtain and display data
Format:
array mysql_fetch_row (resource result_set)
Example:
$query = "select id, name from MyTable order by name";
$result = mysql_query($query);
while (list($id, $name) = mysql_fetch_row ($result)) {
echo("Name: $name ($id)
");
}
Description: The function gets the entire data row from result_set and puts the value in in an indexed array. Usually the list() function is used

9. mysql_fetch_array()-get and display data
format:
array mysql_fetch_array (resource result_set [, int result_type])
Example:
$query = "select id, name from MyTable order by name";
$result = mysql_query($query);
while($row = mysql_fetch_array($result, MYSQL_ASSOC) ) {
$id = $row["id"];
$name = $row["name"];
echo "Name: $name ($id)
" ;
}
Another example:
$query = "select id, name from MyTable order by name";
$result = mysql_query($query);
while($row = mysql_fetch_array ($result, MYSQL_NUM)) {
$id = $row[0];
$name = $row[1];
echo "Name: $name ($id)
}
Note:
The values of result_type are:
MYSQL_ASSOC: The field name represents the key, and the field content is the value
MYSQL_NUM: Numeric index array, the operation is the same as the mysql_fetch_ros() function
MYSQL_BOTH: Returned as an associative array and a numerical index array. The default value of result_type.

10. mysql_fetch_assoc() - Get and display data
Format:
array mysql_fetch_assoc (resource result_set)
Equivalent to calling mysql_fetch_array(resource, MYSQL_ASSOC);

11. mysql_fetch_object()-Get and display data
Format:
object mysql_fetch_object(resource result_set)
Example:
$query = "select id, name from MyTable order by name";
while ($row = mysql_fetch_object($result)) {
$id = $row->id;
$name = $row->name;
echo "Name: $name ($id)
";
}
Description: Returns an object, which is the same as mysql_fetch_array() in operation

12. mysql_num_rows()-The number of selected records
Format:
int mysql_num_rows(resource result_set)
Example:
query = "select id, name from MyTable where id > ; 65";
$result = mysql_query($query);
echo "There are ".mysql_num_rows($result)." records with IDs greater than 65";
Note: Only when determining the select query It is only useful when the number of records obtained.

13. mysql_affected_rows() - the number of records affected by Insert, update, delete
Format:
int mysql_affected_rows([resource link_id])
Example ：
$query = "update MyTable set name='CheneyFu' where id>=5";
$result = mysql_query($query);
echo "The name with ID greater than or equal to 5 has been updated Number of records: ".mysql_affected_rows();
Description: This function gets the number of rows affected by the INSERT, UPDATE or DELETE update statement

14. mysql_list_dbs() - Get database list information
Format:
resource mysql_list_dbs([resource link_id])
Example:
mysql_connect("localhost", "username", "password");
$dbs = mysql_list_dbs();
echo "Databases:
";
while (list($db) = mysql_fetch_rows($dbs)) {
echo "$db
";
}
Description: Display all database names

15. mysql_db_name()-Get the database name
Format:
string mysql_db_name(resource result_set, integer index)
Description: This function obtains the database name located at the specified index in the result_set returned by mysql_list_dbs()

16. mysql_list_tables() - Gets the database table list
Format:
resource mysql_list_tables(string database [, resource link_id])
Example:
mysql_connect("localhost", "username", "password");
$tables = mysql_list_tables("MyDatabase");
while (list($table) = mysql_fetch_row($tables)) {
echo "$table
";
}
Description: This function gets the tables of all tables in the database Name

17. mysql_tablename()-Get a database table name
Format:
string mysql_tablename(resource result_set, integer index)
Example:
mysql_connect("localhost", "username", "password");
$tables = mysql_list_tables("MyDatabase");
$count = -1;
while (++$count < mysql_numrows( $tables)) {
echo mysql_tablename($tables, $count)."
";
}
Description: This function gets the specified index in the result_set returned by mysql_list_tables() Table name

18. mysql_fetch_field()-Get field information
Format:
object mysql_fetch_field(resource result [, int field_offset])
Example:
mysql_connect("localhost", "username", "password");
mysql_select_db("MyDatabase");
$query = "select * from MyTable";
$result = mysql_query($query) ;
$counts = mysql_num_fields($result);
for($count = 0; $count < $counts; $count++) {
$field = mysql_fetch_field($result, $count);
echo "

$field->name $field->type ($field->max_length)

";
}
Description:
The returned object has a total of 12 object attributes:
name: field name
table: table where the field is located
max_length: the maximum length of the field
not_null: if the field cannot is null, it is 1, otherwise 0
primary_key: If the field is the primary key, it is 1, otherwise 0
unique_key: If the field is the unique key, it is 1, otherwise 0
multiple_key: If the field is Non-unique, 1, otherwise 0
numeric: 1 if the field is numeric, otherwise 0
blob: 1 if the field is BLOB, otherwise 0
type: Data type of the field
unsigned: 1 if the field is an unsigned number, 0 otherwise
zerofill: 1 if the field is "zero filled", otherwise 0

19, mysql_num_fields() -Get the number of fields in the query
Format:
integer mysql_num_fields(resource result_set)
Example:
$query = "select id,name from MyTable order by name";
$result = mysql_query($query);
echo "The number of fields in this query is: ".mysql_num_fields($result)."
";

20, mysql_list_fields ()-Get the field names of all fields in the specified table
Format:
resource mysql_list_fields (string database_name, string table_name [, resource link_id])
Example:
$fields =mysql_list_fields( "MyDatabase", "MyTable");
echo "The number of fields in the table MyTable in the database MyDatabase: ".mysql_num_fields($fields)."
";

21 , mysql_field_flags()-Get the specified field option
Format:
string mysql_field_flags (resource result_set, integer field_offset)
Example:
$query = "select id, name from MyTable order by name";
$result = mysql_query($query);
$row=mysql_fetch_wor($row);

22. mysql_field_len()-Get the maximum length of the specified field
Format:
integer mysql_field_len (resource result_set, integer field_offset)
Example:
$query = "select name from MyTable";
$result = mysql_query($query);
$row = mysql_fetch_row($result);
echo mysql_field_len($result, 0)."
";
Explanation:
If mysql_field_len($reseult, 0) = 16777215
Then numer_format(mysql_field_len($result)) is equal to 16,777,215

23. mysql_field_name()-Get the field name
Format:
string mysql_field_name (resource result_set, int field_offset)
Example:
$query = "select id as PKID, name from MyTable order by name";
$result = mysql_query($query);
$row = mysql_fetch_row($result) ;
echo mysql_field_name($result, 0); // Result: PKID

24. mysql_field_type()-Get field type
Format:
string mysql_field_type ( resource result_set, int field_offset)
Example:
$query = "select id, name from MyTable order by name";
$result = mysql_query($query);
$row = mysql_fetch_row($ result);
echo mysql_field_type($result, 0); // Result: int

25. mysql_field_table()-Get the table name of the field
Format:
string mysql_field_table (resource result_set, int field_offset)
Example:
$query = "select id as PKID, name from MyTable order by name";
$result = mysql_query($query);
$row = mysql_fetch_row($result);
echo mysql_field_table($result, 0); // Result: MyTable

MYSQL common functions in PHP (necessary for operating databases under PHP)_PHP tutorial