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