Mysql query to fetch records which are not matched form both tables

Using FULLTEXT indexes has to be handled with great care. Why ? While FULLTEXT index searches do work, the MySQL Query optimizer tends to suggest full table scans if you do not express the query properly.

Let's take your query and look for 'tom'

SELECT DISTINCT c.movieName, c.castName, c.movieImdbId, f.year, f.posterLink
FROM cast_movie as c JOIN film_info as f ON c.ImdbId = f.ImdbId
WHERE c.castName LIKE '%tom%';

This joins everything. Then, it scans the resulting temp table and returns every row with tom.

Let's implement the FULLTEXT method

SELECT DISTINCT c.movieName, c.castName, c.movieImdbId, f.year, f.posterLink
FROM cast_movie as c JOIN film_info as f ON c.ImdbId = f.ImdbId
WHERE MATCH(c.castName) AGAINST ('+tom' IN BOOLEAN MODE);

I can almost assure you that a full table scan will occur during the join because I have experienced it hundreds of times:

• Oct 25, 2011 : FULLTEXT index ignored in BOOLEAN MODE with 'number of words' conditional
• Jan 26, 2012 : Mysql fulltext search my.cnf optimization
• May 07, 2012 : MySQL EXPLAIN doesn't show 'use index' for FULLTEXT
• Jul 18, 2012 : Why full-text-search returns less rows than LIKE

I started writing posts about FULLTEXT and query refactoring ever since I saw a post from webmasterworld.com entitled MySQL Match Against + a very expensive join. How do I optimize this?

Given the information I just mentioned let's take your query and refactor it to handle the FULLTEXT and stilldo a good join.

SELECT DISTINCT c.movieName, c.castName, c.movieImdbId, f.year, f.posterLink
FROM cast_movie as c JOIN film_info as f ON c.ImdbId = f.ImdbId
WHERE MATCH(c.castName) AGAINST ('+tom' IN BOOLEAN MODE);

First, apply the MATCH ... AGAINST operator to cast_movie and return ImdbId and other fields

SELECT ImdbId,movieName,castName,movieImdbId FROM cast_movie
WHERE MATCH(c.castName) AGAINST ('+tom' IN BOOLEAN MODE)

Make that a subquery to provide keys to join and retrieve data from film_info

SELECT DISTINCT c.movieName, c.castName, c.movieImdbId, f.year, f.posterLink FROM
(
    SELECT ImdbId,movieName,castName,movieImdbId FROM cast_movie
    WHERE MATCH(c.castName) AGAINST ('+tom' IN BOOLEAN MODE)
) as c JOIN film_info as f ON c.ImdbId = f.ImdbId;

This should produce a better result.

If your tables use InnoDB Storage Engine, remember to tune the InnoDB Fulltext options. Any fulltext option that does not start with innodb_ is meant for MyISAM (See my post MySQL FullText search on string shorter than 3 chars returns no rows)

Give it a Try !!!

Try this

select a.Date, a.Foo, b.Bar
from TableA a LEFT JOIN TableB b ON a.Date = b.Date
UNION
select b.Date, a.Foo, b.Bar
from TableB b LEFT JOIN TableA a ON a.Date = b.Date

Strictly speaking, the query above does not quite have the same semantics as the original full join, with respect to duplicates. A correct transformation of full join is to a left join union all anti-semi-join:

SELECT 
    TA.TheDate, 
    TA.Foo, 
    TB.Bar
FROM dbo.TableA AS TA
LEFT JOIN dbo.TableB AS TB 
    ON TB.TheDate = TA.TheDate
UNION ALL
SELECT 
    TB.TheDate, 
    Foo = NULL, 
    TB.Bar 
FROM dbo.TableB AS TB
WHERE NOT EXISTS 
(
    SELECT NULL
    FROM dbo.TableA AS TA 
    WHERE TA.TheDate = TB.TheDate
);

This second rewrite will also facilitate the use of an index on TheDate columns.