Specification in like query - mysql

Question

I can't figure out what's wrong with this query. I just want to search in a specific genre, but this query gives me results of other genres. Would really like some help. This code is for my first site built in php.
SELECT *
FROM news
WHERE (titel LIKE '%keyword%') AND genre='politics'

Answer 1

First, I'd suggest reading up on pattern matching in MySQL. The documentation link is: http://dev.mysql.com/doc/refman/5.0/en/pattern-matching.html
SQL pattern matching enables you to use “_” to match any single character and “%” to match an arbitrary number of characters (including zero characters). In MySQL, SQL patterns are case-insensitive by default. Some examples are shown here. You do not use = or <> when you use SQL patterns; use the LIKE or NOT LIKE comparison operators instead.
Examples
To find names beginning with “b”:
mysql> SELECT * FROM pet WHERE name LIKE 'b%';
+--------+--------+---------+------+------------+------------+
| name | owner | species | sex | birth | death |
+--------+--------+---------+------+------------+------------+
| Buffy | Harold | dog | f | 1989-05-13 | NULL |
| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |
+--------+--------+---------+------+------------+------------+
To find names ending with “fy”:
mysql> SELECT * FROM pet WHERE name LIKE '%fy';
+--------+--------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+--------+--------+---------+------+------------+-------+
| Fluffy | Harold | cat | f | 1993-02-04 | NULL |
| Buffy | Harold | dog | f | 1989-05-13 | NULL |
+--------+--------+---------+------+------------+-------+
To find names containing a “w”:
mysql> SELECT * FROM pet WHERE name LIKE '%w%';
+----------+-------+---------+------+------------+------------+
| name | owner | species | sex | birth | death |
+----------+-------+---------+------+------------+------------+
| Claws | Gwen | cat | m | 1994-03-17 | NULL |
| Bowser | Diane | dog | m | 1989-08-31 | 1995-07-29 |
| Whistler | Gwen | bird | NULL | 1997-12-09 | NULL |
+----------+-------+---------+------+------------+------------+
To find names containing exactly five characters, use five instances of the “_” pattern character:
mysql> SELECT * FROM pet WHERE name LIKE '_____';
+-------+--------+---------+------+------------+-------+
| name | owner | species | sex | birth | death |
+-------+--------+---------+------+------------+-------+
| Claws | Gwen | cat | m | 1994-03-17 | NULL |
| Buffy | Harold | dog | f | 1989-05-13 | NULL |
+-------+--------+---------+------+------------+-------+
Your modified query
So, you want your query to select rows from the NEWS table and select everything where the TITLE is like a keyword and GENRE is equal to a particular string.
Following is how I would structure your query. Performance considerations are not present in this query, but you may want to investigate indexes and other performance enhancers if this is a frequent query on a large table.
Originally, you are using:
SELECT * FROM news WHERE (title LIKE '%keyword%') AND genre='politics'
Option 1:
SELECT *
FROM news
WHERE
title LIKE '%keyword%'
AND
genre = 'politics';
Option 2:
You should think about where your input is coming from and if you need to parameterize the fields before you insert them into your query. Using parameters can lead to cleaner, more flexible code as well providing security and type checking.
Try something like this. This untested code, so there might be some syntax issues, but it should be close.
private string title = "%title%";
private string genre = "genre";
using (MySqlConnection con = new MySqlConnection(connectionString))
{
using (MySqlCommand cmd = new MySqlCommand())
{
cmd.Connection = con;
cmd.CommandText
= "SELECT * FROM NEWS WHERE TITLE LIKE '#title' AND GENRE = #genre; ";
cmd.Parameters.AddWithValue("#title", title);
cmd.Parameters.AddWithValue("#genre", genre);
using (MySqlDataReader drd = cmd.ExecuteReader())
{
while (drd.Read())
{
// Read from data reader
}
}
}
}