SQL WHERE CLAUSE PAGE 15

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SQL WHERE CLAUSE

SQL WHERE Clause 


The SQL WHERE clause is used to specify a condition while fetching 
the data from single table or joining with multiple tables. 
If the given condition is satisfied, then only it returns specific 
value from the table. You would use WHERE clause to filter the records
 and fetching only necessary records. 
The WHERE clause is not only used in SELECT statement, but it is 
also used in UPDATE, DELETE statement, etc., which we would examine
 in subsequent chapters. 
Syntax: 
The basic syntax of SELECT statement with WHERE clause is as follows: 
SELECT column1, column2, columnN  
FROM table_name 
WHERE [condition] 
You can specify a condition using comparison or logical operators 
like >, <, =, LIKE, NOT etc. Below examples would make this concept clear. 
Example: 
Consider the CUSTOMERS table having the following records: 
+----+----------+-----+-----------+----------+ 
| ID | NAME     | AGE | ADDRESS   | SALARY   | 
+----+----------+-----+-----------+----------+ 
|  1 | Ramakrishna  |  32 | Ahmedabad |  2000.00 | 
|  2 | Mdhu sudhan rao   |  25 | Delhi     |  1500.00 | 
|  3 | Sai  |  23 | Kota      |  2000.00 | 
|  4 | Kishor  |  25 | Mumbai    |  6500.00 | 
|  5 | Ranjith    |  27 | Bhopal    |  8500.00 | 
|  6 | Abhi    |  22 | MP        |  4500.00 | 
|  7 | Kumar     |  24 | Indore    | 10000.00 | 
+----+----------+-----+-----------+----------+ 
Following is an example, which would fetch ID, Name and 
Salary fields from the CUSTOMERS table where salary is 
greater than 2000: 
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SQL> SELECT ID, NAME, SALARY  
FROM CUSTOMERS 
WHERE SALARY > 2000; 
This would produce the following result: 
+----+----------+----------+ 
| ID | NAME     | SALARY   | 
+----+----------+----------+ 
|  4 | Kishor  |  6500.00 | 
|  5 | Ranjith    |  8500.00 | 
|  6 | Abhi    |  4500.00 | 
|  7 | Kumar     | 10000.00 | 
+----+----------+----------+ 
Following is an example, which would fetch ID, Name and 
Salary fields from the CUSTOMERS table for a customer 
with name Ranjith . Here, it is important to note that 
all the strings should be given inside single quotes ('')
 where as numeric values should be given without any 
quote as in above example: 
SQL> SELECT ID, NAME, SALARY  
FROM CUSTOMERS 
WHERE NAME = 'Ranjith '; 
This would produce the following result: 
+----+----------+----------+ 
| ID | NAME     | SALARY   | 
+----+----------+----------+ 
|  5 | Ranjith    |  8500.00 | 
+----+----------+----------+