sql server coalesce函数 优缺点 sqlserver函数大全 聚合函数对一组值计算后返回单个值。除了count(统计项数)函数以外,其他的聚合函数在计算式都会忽略空值(null)。所有的聚合函数均为确定性函数。即任何时候使用一组相同的输入值调用聚合函数执行后的返回值都是相同的,无二义性。 聚合函数通常会在下列场合使用。 1、...
NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0) PRIMARYKEY, col3ASISNULL(col1,0) );-- This statement succeeds because the nullability of the-- ISNULL function evaluates AS NOT NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0), col3ASISNULL(col1,0) PRIMARY...
SQL SELECTCASEWHENxISNOTNULLTHENxELSE1ENDFROM(SELECT(SELECTNullableFROMDemoWHERESomeCol =1)ASx)AST; Compare COALESCE and ISNULL TheISNULLfunction and theCOALESCEexpression have a similar purpose but can behave differently. BecauseISNULLis a function, it's evaluated only once. As described previously...
NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0) PRIMARYKEY, col3ASISNULL(col1,0) );-- This statement succeeds because the nullability of the-- ISNULL function evaluates AS NOT NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0), col3ASISNULL(col1,0) PRIMARY...
COALESCE is a SQL function that returns the first non-NULL expression among its arguments. It is often used to handle NULL values and provide a default value when a NULL is encountered. ## Steps to Use COALESCE in SQL Server Here are the steps to use COALESCE in SQL Server: ...
To determine the total amount paid to all employees, use the COALESCE function to receive only the nonnull value found in the hourly_wage, salary, and commission columns. SELECT CONVERT(money, COALESCE(null, 5, null, 40 * 52, 65, null)) AS "First nonnull value"...
CREATE TABLE #Demo ( col1 INT NULL, col2 AS COALESCE (col1, 0) PRIMARY KEY, col3 AS ISNULL(col1, 0) ); -- This statement succeeds because the nullability of the -- ISNULL function evaluates AS NOT NULL. CREATE TABLE #Demo ( col1 INT NULL, col2 AS COALESCE (col1, 0), col...
NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0) PRIMARYKEY, col3ASISNULL(col1,0) );-- This statement succeeds because the nullability of the-- ISNULL function evaluates AS NOT NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0), col3ASISNULL(col1,0) PRIMARY...
To determine the total amount paid to all employees, use the COALESCE function to receive only the nonnull value found in the hourly_wage, salary, and commission columns.Copy SELECT CONVERT(money, COALESCE(null, 5, null, 40 * 52, 65, null)) AS "First nonnull value" ...
NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0) PRIMARYKEY, col3ASISNULL(col1,0) );-- This statement succeeds because the nullability of the-- ISNULL function evaluates AS NOT NULL.CREATETABLE#Demo ( col1INTNULL, col2ASCOALESCE(col1,0), col3ASISNULL(col1,0) PRIMARY...