Gaia Posted October 29, 2005 Share Posted October 29, 2005 hey, I know there are ways to join information in 2 or more tables by using LEFT/RIGHT JOIN MySQL commands. I've read the mysql.com documentation on it and it still confuses me. I don't understand why there are single letters placed before the table name ( m.foo, s.boo ) etc. Does anyone have a tutorial or site that explains LEFT/RIGHT JOIN alittle better? Thanks Quote Link to comment https://forums.phpfreaks.com/topic/2756-joining-tables/ Share on other sites More sharing options...
obsidian Posted October 29, 2005 Share Posted October 29, 2005 not really a tutorial, but i think i might be able to help you understand a bit better... whenever you declare a table name in a SQL statement, you can name the table whatever you want. usually people use a single letter to help shorten their code. when you are referencing two tables that have the same field name, you must declare a table name before that field name since it would be a duplicate reference otherwise. for instance: [!--sql--][div class=\'sqltop\']SQL[/div][div class=\'sqlmain\'][!--sql1--][span style=\'color:blue;font-weight:bold\']SELECT[/span] * FROM table1, table2 WHERE table1.id = '$id' AND table2.user = table1.id; [!--sql2--][/div][!--sql3--] this can also be written like this (notice the letters and references are different: [!--sql--][div class=\'sqltop\']SQL[/div][div class=\'sqlmain\'][!--sql1--][span style=\'color:blue;font-weight:bold\']SELECT[/span] * FROM table1 a, table2 b WHERE a.id = '$id' AND b.user = a.id; [!--sql2--][/div][!--sql3--] hope this helps Quote Link to comment https://forums.phpfreaks.com/topic/2756-joining-tables/#findComment-9237 Share on other sites More sharing options...
Gaia Posted October 29, 2005 Author Share Posted October 29, 2005 Thanks for the explination. I finally understand it! Just on more question. I noticed you didn't use a LEFT/RIGHT JOIN in there. What specifically would those be used for and would you mind creating a query with on of them in it and exlaining it to me like you did in your last post? Thanks, i really appreciate it Quote Link to comment https://forums.phpfreaks.com/topic/2756-joining-tables/#findComment-9239 Share on other sites More sharing options...
Barand Posted October 29, 2005 Share Posted October 29, 2005 In this query SELECT * FROM table1 a, table2 b WHERE a.id = '$id' AND b.user = a.id; the WHERE clause is specifying the join condition (b.user = a.id) This is an alternative syntax and is equivalent to SELECT * FROM table1 a INNER JOIN table2 b ON b.user = a.id WHERE a.id = '$id' I always recommend the latter 1 ) it produces faster queries 2 ) it separates the relationship info from the search criteria and IMO shows more clearly what the query is doing. Quote Link to comment https://forums.phpfreaks.com/topic/2756-joining-tables/#findComment-9245 Share on other sites More sharing options...
Gaia Posted October 30, 2005 Author Share Posted October 30, 2005 hmm ok i think i'm starting to understand this alittle better. I will mark this solved until i come across any more questions while trying it out Quote Link to comment https://forums.phpfreaks.com/topic/2756-joining-tables/#findComment-9266 Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.