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    <p>For Example if you are trying to get A country's Name by using Country_ID in this Project table shown in your question, You could do something like </p> <pre><code>SELECT C.CountryName_Colummn, C.SomeOtheColumn, ...... FROM Projects P INNER JOIN Countries C ON P.id_Country = C.id_Country WHERE SomeColum = 'Your Condition' </code></pre> <p>1) SELECT Clause you select the columns you need in your result set.<br/> 2) FROM you Mention table(s) name(s) <br/> 3) ON Clause you define the relationship between the tables Say Projects table had a Column id_Country which refers to id_Country in Countries table defines the relationship between these two tables.<br/> 4) After you have Selected the column list, Source of data (tables), Their relationship (On Clause) then you can filter the number of rows returning from you query, like you can something like id_Country<br/> WHERE C.CountryName = 'UK' will return results only from UK.<br/> 5) In from Clause the Letters 'C' and 'P' are alias so we dont have to type full table names again n again, makes our code simpler and easier to read and debug. <br/></p> <p>No matter how many tables you have to join to get the required data as long as you can define the relationship between them table in your query it should work fine. SQL server rarely you would find all the required data in one table normally you would join 2-3 tables or more tables. For example you want some data that is present in 3 different tables you would join them all three in one query something like this ...</p> <pre><code>SELECT C.CountryName_Colummn, C.SomeOtheColumn, ...... FROM Projects P INNER JOIN Countries C ON P.id_Country = C.id_Country INNER JOIN Table_3_Name T3 ON T3.CommonColumn = P.SomeCommonColumn (it will be a common column between table 3 and Projects OR Countries) WHERE SomeColum = 'Your Condition' </code></pre> <p>But you really need to look in joins as you can do different types of joins between tables, Hers in this example I used INNER JOIN which returns only the matching rows between all these tables, you could do LEFT JOIN or RIGHT JOIN.<br /> <strong>LEFT JOIN</strong> returns all the rows from the table on LEFT side of the JOIN key word and only matching rows from other tables.<br/> <strong>RIGHT JOIN</strong> returns all the rows from the on the right side of the JOIN key word and only mantching rows from other tables. </p> <p><strong>Queries with only desired Columns</strong></p> <pre><code>Select customers.customer_name, Products.Product_type, Manufacturers.Manuf_name from Projects inner join customers on customers.cust_id= Projects.proj_cust_id inner join Products on Products.prod_id= Projects.proj_prod_id inner join Manufacturers on Manufacturers.man_id= Projects.proj_man_id </code></pre> <p>Making use of Alias will give you exactly the same reuslt but easy to read code also try this ....</p> <pre><code>Select C.customer_name, Prod.Product_type, M.Manuf_name from Projects Proj inner join customers C on C.cust_id= Proj.proj_cust_id inner join Products Prod on Prod.prod_id= Proj.proj_prod_id inner join Manufacturers M on M.man_id= Proj.proj_man_id </code></pre>
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    1. POHow to get referenced values from another table?
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    1. COBecause I have 3 of those situations on one table that requires the inner join (prod, cuts, man) to other 3 tables, should I make 3 queries (starting with select, or combine all of them?
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    2. COBut I think you really need to do a little bit of study and its really not that hard, if you will be working on sql in future you really need to get good understanding of joins as I cant think of a query in past year or so in which all the data I needed was in one table :)
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    3. COThat is granted. I am busy studying it. Thanks.
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