平面构成解构与重构图:SqlServer数据库语句大全（六）

5.数据库函数Functions
5.1转换函数Data Convert Functions
5.2聚集函数Aggregate Functions
5.3字符函数char Functions
5.4日期函数Date Functions
5.5数学函数Math Functions
5.6分析函数Analytical Functions
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5.1转换函数Data Convert Functions
5.1.1 CAST()
功能:数据类型转换
语法:CAST(expression AS data_type)
代码:
SELECT BillingDate,
BillingTotal,
CAST(BillingDate AS varchar) AS varcharDate,
CAST(BillingTotal AS int) AS integerTotal,
CAST(BillingTotal AS varchar) AS varcharTotal
FROM Billings
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5.1.2 COALESCE()
功能:返回表达式列表中第一个非空值表达式的值
语法:COALESCE(expression1, expression2, ... expressionN)
代码:
SELECT BankerName,
COALESCE(CAST(BillingTotal AS varchar), 'No Billings') AS BillingTotal
FROM Bankers LEFT JOIN Billings
ON Bankers.BankerID = Billings.BankerID
ORDER BY BankerName

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5.1.3 CONVERT()
功能:把表达式值转换为指定sytle的数据类型
语法:CONVERT(data_ type(), expression,