Someone please help me with sql

[krahny]

I was wondering if anyone knows what the sql select command will return in a query if it finds no match. Or, maybe there's a way to check if a record exists with a certain value.

Somone please help.

[diabolo]

Or, maybe there's a way to check if a record exists with a certain value.

SELECT column_name(s) FROM table_name WHERE column_name operator value

http://www.w3schools.com/sql/sql_where.asp

[krahny]

I know that code, but I need to know what it returns if it finds no match to the value.

Thanks anyway.

[Gouri]

Handling in PHP

For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query() returns a resource on success, or FALSE on error.


Only SQL

Empty set (0.00 sec)

[descalzo]

PHP:

 
# $dbh is the connection to your database
 
$sql = "SELECT name, city  FROM customer_table WHERE state='CA' " ;
 
$result = mysqli_query(  $dbh , $sql ) ;
 
if( $result === false ){
   # HANDLE ERROR ;
} elseif ( mysqli_num_rows( $result ) == 0 ) {
   # HANDLE  NO MATCH 
} else {
   # HANDLE AT LEAST ONE MATCH
} 

[misson]

I know that code, but I need to know what it returns if it finds no match to the value.

Notionally, the empty set. Relational DBMSs, such as MySQL, are modeled after relationships, which are relations ([2]) where you don't care about domain order. In RDB parlance, "table" is synonymous with "relationship". An SQL statement creates a new relationship by joining, filtering and sorting other relationships. If a join or a filter results in no tuples (rows), the result is an empty set.

In PHP, the various MySQL drivers invariably return a result with no rows. If you want to test for an empty result, use (e.g.) mysqli_num_rows or PDOStatement::rowCount.

[krahny]

Thanks for your help!

That code descalzo gave me worked Great!!