使用mysql的select语句查询结果集

Summary: in this tutorial, you will learn how to MySQL SELECT statement to query data from a database table.

The MySQL SELECT statement allows you to retrieve zero or more rows from tables or views. The SELECT statement is the one of the most commonly used queries in MySQL.

The SELECT statement returns a result that is a combination of columns and rows, which is also known as a result set.

MySQL SELECT syntax

The following illustrates the syntax of the SELECT statement:

SELECT column_1,column_2... FROM table_1 [INNER | LEFT |RIGHT] JOIN table_2 ON conditions WHERE conditions GROUP BY group  HAVING group_conditions ORDER BY column_1 [ASC | DESC] LIMIT offset, row_count

The SELECT statement is composed of several clauses:

• SELECT chooses which columns of  the table you want to get the data.

• FROM specifies the table from which you get the data.

• JOIN gets data from multiple table based on certain join conditions.

• WHERE filters rows to select.

• GROUP BY group rows to apply aggregate functions on each group.

• HAVING filters group based on groups defined by GROUP BY clause.

• ORDER BY specifies the order of the returned result set.

• LIMIT constrains number of returned rows.

You will learn about each clause in more detail in the next tutorial. In this tutorial, we are going to focus on the simple form of the SELECT statement.

MySQL SELECT Examples

To select all columns and rows from the employees table, you use the following query:

SELECT * FROM employees

The asterisk (*) notation is a shorthand of selecting all columns in the table.

The SELECT statement also allows you to query partial data of a table by specifying a list of comma-separated columns in the SELECT clause. For example, if you want to view only first name, last name and job title of the employees,  you use the following query:

SELECT lastname,        firstname,        jobtitle FROM employees

In this tutorial, you’ve learned about the basic MySQL SELECT statement to query data from a database table in MySQL

Related Tutorials

• Combining Result Sets by Using MySQL UNION

• MySQL BETWEEN Operator Explained

• MySQL Copy Table

• MySQL LEFT JOIN

• MySQL GROUP BY

• MySQL HAVING

• Querying Data with MySQL IN Operator

• Using MySQL LIKE Operator to Select Data Based On Patterns

• How to Use MySQL DISTINCT to Eliminate Duplicate Rows

• Using MySQL LIMIT

• MySQL INNER JOIN

原文链接：http://outofmemory.cn/mysql/mysql-select-statement-query-data