An expression is a combination of one or more values, operators, and SQL functions that evaluate to a value.

SQL expressions are like formulas and they are written in query language. You can also use to query the database for a specific set of data.

Syntax

Consider the basic syntax of the SELECT statement as follows −

SELECT column1, column2, columnN 
FROM table_name 
WHERE [CONDITION | EXPRESSION];

Following are the different types of SQLite expressions.

SQLite – Boolean Expressions

SQLite Boolean Expressions fetch the data on the basis of matching single value. Following is the syntax −

SELECT column1, column2, columnN 
FROM table_name 
WHERE SINGLE VALUE MATCHTING EXPRESSION;

Consider COMPANY table with the following records −

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0

Following is a simple examples showing the usage of SQLite Boolean Expressions −

sqlite> SELECT * FROM COMPANY WHERE SALARY = 10000;

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
4           James        24          Houston   10000.0

SQLite – Numeric Expression

These expressions are used to perform any mathematical operation in any query. Following is the syntax −

SELECT numerical_expression as OPERATION_NAME
[FROM table_name WHERE CONDITION] ;

Here, numerical_expression is used for mathematical expression or any formula. Following is a simple example showing the usage of SQLite Numeric Expressions.

sqlite> SELECT (15 + 6) AS ADDITION
ADDITION = 21

There are several built-in functions such as avg(), sum(), count(), etc., to perform what is known as aggregate data calculations against a table or a specific table column.

sqlite> SELECT COUNT(*) AS "RECORDS" FROM COMPANY; 
RECORDS = 7

SQLite – Date Expressions

Date Expressions returns the current system date and time values. These expressions are used in various data manipulations.

sqlite> SELECT CURRENT_TIMESTAMP;
CURRENT_TIMESTAMP = 2013-03-17 10:43:35