nabeel21 Posted October 20, 2003 Share Posted October 20, 2003 I have two tables: 1. tb1 2. tb2 They share the same column called \"County\". I want to select all entries from tb1 that are NOT in tb2. E.g. If a county \"xyz\" is in tb2 then i dont want it to show up when i run the query on tb1. Quote Link to comment https://forums.phpfreaks.com/topic/1188-join-two-tables/ Share on other sites More sharing options...
bigdoggy59 Posted October 20, 2003 Share Posted October 20, 2003 I took this right out of the MySQL Manual. Hope it helps. If there is no matching record for the right table in the ON or USING part in a LEFT JOIN, a row with all columns set to NULL is used for the right table. You can use this fact to find records in a table that have no counterpart in another table: mysql> select table1.* from table1 LEFT JOIN table2 ON table1.id=table2.id where table2.id is NULL; This example finds all rows in table1 with an id value that is not present in table2 (that is, all rows in table1 with no corresponding row in table2). This assumes that table2.id is declared NOT NULL, of course. See section 12.5.5 How MySQL Optimizes LEFT JOIN and RIGHT JOIN. Quote Link to comment https://forums.phpfreaks.com/topic/1188-join-two-tables/#findComment-3988 Share on other sites More sharing options...
nabeel21 Posted October 20, 2003 Author Share Posted October 20, 2003 Here are 2 tables which share the same columns (CITY and COUNTY) TB1 (Main table that stores the info of all cities and counties) CITY-------------------------COUNTY --------------------------------------- Tampa----------------------Hillsborough Orlando---------------------Orange Frostproof-------------------Polk Arcadia----------------------Desoto County----------------------Collier Tallahassee-----------------Leon ---------------------------------------------- TB2 (Contains info for all cities and counties who have submitted data) CITY--------------------------COUNTY --------------------------------------- Arcadia----------------------Desoto County----------------------Collier Tallahassee-----------------Leon ------------------------------------------------ Now I want to query TB1 and find out which city/county has NOT submitted their data. The query should return CITY-------------------------COUNTY ---------------------------------------- Tampa----------------------Hillsborough Orlando---------------------Orange Frostproof------------------Polk Thanks in advance. Quote Link to comment https://forums.phpfreaks.com/topic/1188-join-two-tables/#findComment-3991 Share on other sites More sharing options...
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