The WHERE clause is an important part of SQL (Structured Query Language), which is used to extract data from a database. The WHERE clause is used to filter the rows of data returned by a SELECT statement, based on a specified condition.
The syntax of the WHERE clause is as follows:
SELECT column1, column2, ... FROM table_name WHERE condition;
Here, “column1, column2, …” are the columns of the table you want to retrieve data from. “table_name” is the name of the table you want to retrieve data from. The “condition” specifies the criteria that must be met for the rows to be returned.
For example, if you want to retrieve all the records from the “orders” table where the order amount is greater than 1000, you can use the following SQL statement:
SELECT * FROM orders WHERE order_amount > 1000;
This SQL statement will return all the records from the “orders” table where the value in the “order_amount” column is greater than 1000.
You can use various operators in the WHERE clause to specify different conditions. Some of the commonly used operators are:
Comparison operators: =, <, >, <=, >=, !=
Logical operators: AND, OR, NOT
IN operator: allows you to specify a list of values to match against
LIKE operator: allows you to perform pattern matching using wildcards
BETWEEN operator: allows you to retrieve records that fall within a range of values.
In addition, you can use parentheses to group conditions and specify the order of evaluation.
In conclusion, the WHERE clause is a powerful feature of SQL that allows you to retrieve specific data from a table based on specified conditions. With the right use of operators and conditions, you can extract exactly the information you need from a database.