inner-join

For example, I have 3 tables: user , group and permission , and two many2many relationships between them: user_groups and group_permissions . I need to select all permissions of given user, without repeats. Every time I encounter a similar problem, I can not determine which version of a query better: SELECT permisson_id FROM group_permission WHERE EXISTS( SELECT 1 FROM user_groups WHERE user_groups.user_id = 42 AND user_groups.group_id = group_permission.group_id ) SELECT DISTINCT permisson_id FROM group_permission INNER JOIN user_groups ON user_groups.user_id = 42 AND user_groups.group_id =

This question already has an answer here: Difference between JOIN and INNER JOIN 6 answers I can't find documentations on the key word join but I saw examples on the web using it. I was doing some experiment with it in Oracle hr schema, where I have table departments : deparment_name manager_id location_id A table employees : first_name employee_id And table locations : location_id city Query should return the department_name, first_name of the manager of the department, and the city where the department is located. The code using the keyword join seem to return the some result in comparison

I have a question about configuring Map/Side inner join for multiple mappers in Hadoop. Suppose I have two very large data sets A and B, I use the same partition and sort algorithm to split them into smaller parts. For A, assume I have a(1) to a(10), and for B I have b(1) to b(10). It is assured that a(1) and b(1) contain the same keys, a(2) and b(2) have the same keys, and so on. I would like to setup 10 mappers, specifically, mapper(1) to mapper(10). To my understanding, Map/Side join is a pre-processing task prior to the mapper, therefore, I would like to join a(1) and b(1) for mapper(1),

I am using this query: SELECT a.sales_id, d.bus_title, a.cat_id FROM tbl_sales a INNER JOIN tb_category b ON a.cat_id = b.cat_id INNER JOIN tbl_business d ON d.bus_id = a.bus_id which produces this result: sales_id | bus_title |cat_id ----------|----------------|------------ 1 | Business 1 | 6 2 | Business 12 | 12 3 | Business 123 | 25 I changed the field cat_id into a new table named tb_sales_category which contains the fields sales_category_id , sales_id , cat_id . How can I write the new query by joining this table too to, get the same result as above? I am kind of new to databases, need

So I have four tables. Each table has a single id for the previous table id. So my in click table has an id and an id for the ad from which it came. In the ad table, it has an id for the ad and one for the campaign it's from. So here's an example. Table4 - id company table_id 11 hp 20 12 apple 23 13 kohls 26 14 target 21 15 borders 28 Table3 - id value table2_id 21 ks 53 22 al 54 23 tx 53 24 fl 55 25 co 51 Table2 - id value table1_id 51 ks 34 52 al 34 53 tx 33 54 fl 35 55 co 31 Table1 - id value 31 ks 32 al 33 tx 34 fl 35 co So to find out where the values in Table 4 came from, I need to work

I have 2 servers one servers runs Microsoft SQL Server and the other one is using MySql. I need to be able to inner join a table from MS SQL name it "A" to a table "B" located on a different server that uses MySql So I want to be able to do something like this SELECT A.*, B.* FROM A INNER JOIN B ON A.id=B.id LIMIT 100 How can I do this? note that both servers are on the same network. 1st link on google states... you need to install this: http://www.mysql.com/products/connector/ and follow this guide: http://technikhil.wordpress.com/2007/05/13/getting-microsoft-sql-server-and-mysql-to-talk/ to