SQL NON EQUI JOIN
NON EQUI JOIN
The SQL NON EQUI JOIN uses comparison operator instead of the equal sign like >, <, >=, <= along with conditions.
SELECT * FROM table_name1, table_name2 WHERE table_name1.column [> | < | >= | <= ] table_name2.column;
Here is an example of non equi join in SQL between two tables
Sample table: orders
Sample table: customer
To get order number and order amount columns from orders table aliased as 'a' and customer name and working area columns from customer table aliased as 'b' after joining said two tables with the following condition -
1. order amount of orders table matches any of the opening amounts of customer table,
the following SQL statement can be used:
SELECT a.ord_num,a.ord_amount,b.cust_name,b.working_area FROM orders a,customer b WHERE a.ord_amount BETWEEN b.opening_amt AND b.opening_amt;
ORD_NUM ORD_AMOUNT CUST_NAME WORKING_AREA --------- ---------- ---------------------------------------- ------------- 200110 3000 Micheal New York 200101 3000 Micheal New York 200108 4000 Cook London 200119 4000 Cook London 200113 4000 Cook London 200108 4000 Karl London 200119 4000 Karl London 200113 4000 Karl London
Key points to remember
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Here is a new document which is a collection of questions with short and simple answers, useful for learning SQL as well as for interviews.
Practice SQL Exercises
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SQL: Interview question/Tips of the Day
First Normal Forms
- Eliminate repeating groups in individual tables.
- Create a separate table for each set of related data.
- Identify each set of related data with a primary key.
Do not use multiple fields in a single table to store similar data. For example, to track an inventory item that may come from two possible sources, an inventory record may contain fields for Vendor Code 1 and Vendor Code 2. Also, what happens when you add a third vendor? Adding a field is not the answer; it requires program and table modifications and does not smoothly accommodate a dynamic number of vendors. Instead, place all vendor information in a separate table called Vendors, then link inventory to vendors with an item number key, or vendors to inventory with a vendor code key.
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