SQL SELECT and SELECT WHERE
The SELECT statement is the most commonly used SQL statement and is used to retrieve data from one or more tables in a database. The basic syntax of a SELECT statement is as follows:
SELECT column1, column2, ..., columnN FROM table_name;
In this syntax, column1
, column2
, ..., columnN
are the names of the columns that you want to retrieve from the table. table_name
is the name of the table that contains the columns.
For example, to retrieve all the data from a table named employees
and display it in the result set, you would use the following SELECT statement:
SELECT * FROM employees;
The asterisk (*) is a wildcard character that represents all the columns in the table. This statement retrieves all the data from the employees
table.
The WHERE clause is used to filter the data returned by the SELECT statement. The basic syntax of a SELECT statement with a WHERE clause is as follows:
SELECT column1, column2, ..., columnN FROM table_name WHERE condition;
In this syntax, condition
is an expression that evaluates to true or false. Only the rows that satisfy the condition are returned in the result set.
For example, to retrieve all the data from the employees
table where the salary
column is greater than or equal to 50000, you would use the following SELECT statement with a WHERE clause:
SELECT * FROM employees WHERE salary >= 50000;
This statement retrieves all the rows from the employees
table where the value of the salary
column is greater than or equal to 50000. The result set contains only the rows that satisfy this condition.