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文件名称：选择查询出的行-SQL语言基础
文件大小：5.26MB
文件格式：PPT
更新时间：2021-04-25 19:38:09
SQL 基础
选择查询出的行
*
SELECT [DISTINCT] {*| column [alias], ...}
FROM table
[WHERE condition(s)];
用where子句限定查询出的行.
Where子句紧跟在From子句之后.
*
条件最常见的形式是由变量、常量和比较运算符组成。
Limiting Rows Selected
You can restrict the rows returned from the query by using the WHERE clause. A WHERE clause contains a condition that must be met, and it directly follows the FROM clause.
In the syntax:
WHERE restricts the query to rows that meet a condition
condition is composed of column names, expressions, constants, and a comparison operator
The WHERE clause can compare values in columns, literal values, arithmetic expressions, or functions. The WHERE clause consists of three elements:
Column name
Comparison operator
Column name, constant, or list of values