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文件名称:单行函数-SQL语言基础
文件大小:5.26MB
文件格式:PPT
更新时间:2021-04-25 19:38:12
SQL 基础
单行函数
*
function_name (column|expression, [arg1, arg2,...])
操作数据项
接收参数并返回一个值
在返回的每一行上进行处理
每一行都有一个处理结果
可能要修改数据类型
可以进行嵌套
接受多个参数,参数可以是一个列或者一个表达式
*
Single-Row Functions
Single-row functions are used to manipulate data items. They accept one or more arguments and return one value for each row returned by the query. An argument can be one of the following:
User-supplied constant
Variable value
Column name
Expression
Features of single-row functions:
Act on each row returned in the query
Return one result per row
May return a data value of a different type than that referenced
May expect one or more arguments
Can be used in SELECT, WHERE, and ORDER BY clauses; can be nested
In the syntax:
function_name is the name of the function
column is any named database column
expression is any character string or calculated expression
arg1, arg2 is any argument to be used by the function