anti-join

I have two tables and I would like to append them so that only all the data in table A is retained and data from table B is only added if its key is unique (Key values are unique in table A and B however in some cases a Key will occur in both table A and B). I think the way to do this will involve some sort of filtering join (anti-join) to get values in table B that do not occur in table A then append the two tables. I am familiar with R and this is the code I would use to do this in R. library("dplyr") ## Filtering join to remove values already in "TableA" from "TableB" FilteredTableB <- anti

I have two tables that are joined together. A has many B Normally you would do: select * from a,b where b.a_id = a.id To get all of the records from a that has a record in b. How do I get just the records in a that does not have anything in b? select * from a where id not in (select a_id from b) Or like some other people on this thread says: select a.* from a left outer join b on a.id = b.a_id where b.a_id is null select * from a left outer join b on a.id = b.a_id where b.a_id is null Another approach: select * from a where not exists (select * from b where b.a_id = a.id) The "exists" approach

My tables are set up something like this: table name: process fields: name, id_string table name: value_seach fields: id_string, value I want to construct a select statement that will display all of the process names (with it's respective id_string) that do not have an entry in value_search. The id_string in the process table can be null , and still have a name, but those need to be excluded if possible. The id_string in value_search can never be null How do I do this? In general if you want rows that don't exist in another table, then LEFT JOIN the other table and WHERE ... IS NULL to a

I have two tables TABLE1 which looks like: id name address 1 mm 123 2 nn 143 and TABLE2 w/c looks like: name age mm 6 oo 9 I want to get the non existing names by comparing the TABLE1 with the TABLE2 . So basically, I have to get the 2nd row, w/c has a NN name that doesn't exist in the TABLE2 , the output should look like this: id name address 2 nn 143 I've tried this but it doesn't work: SELECt w.* FROM TABLE1 W INNER JOIN TABLE2 V ON W.NAME <> V.NAME and it's still getting the existing records. An INNER JOIN doesn't help here. One way to solve this is by using a LEFT JOIN : SELECT w.* FROM