MySQL Tutorials - Herong's Tutorial Examples - v4.46, by Herong Yang
SELECT Statements
A tutorial example is provided on how to use SELECT statements to retrieve from database as multiple rows and multiple fields in each row.
A select statement is also called a query statement. It is normally used to retrieve rows of data selected from specified tables. The generic syntax of a select statement is:
SELECT select_expression_list [FROM clause]
where "expression_list" defines a list of select expressions, and "FROM clause" defines a select table with rows and columns of values. Column names of the select table can be used as variables in select expressions to represent column values in each row.
When a select statement is executed, a nested loop logic will be performed to generate rows of output data:
Loop on each row of the select table, do: Loop on each select expression, do: Evaluate this expression with possible column values in current row of the select table. End of loop Return the results of all select expressions as a row of output data End of loop
Note:
Sample select statements without FROM clause:
SELECT 'Hello world!'; SELECT 'Apple', 'Orange'; SELECT CHAR_LENGTH('Hello world!'); SELECT 1, 4, 9, 16, 25; SELECT PI(); SELECT CURRENT_DATE(), CURRENT_TIME();
Table of Contents
MySQL Introduction and Installation
Introduction of MySQL Programs
Perl Programs and MySQL Servers
Java Programs and MySQL Servers
Character Strings and Bit Strings
Table Column Types for Different Types of Values
Using DDL to Create Tables and Indexes
Using DML to Insert, Update and Delete Records
►Using SELECT to Query Database
FROM Clause of a SELECT Statement
JOIN - Operation to Join Two Tables
JoinTable.sql - Example of Join Tables
WHERE Clause of a SELECT Statement
ORDER BY Clause of a SELECT Statement
GROUP BY Clause of a SELECT Statement
Window Functions for Statistical Analysis
Use Index for Better Performance
Transaction Management and Isolation Levels
Defining and Calling Stored Procedures
Variables, Loops and Cursors Used in Stored Procedures
System, User-Defined and Stored Procedure Variables
Storage Engines in MySQL Server
InnoDB Storage Engine - Primary and Secondary Indexes
Performance Tuning and Optimization
Installing MySQL Server on Linux