coalesce 订阅
COALESCE是一个函数, (expression_1, expression_2, ...,expression_n)依次参考各参数表达式,遇到非null值即停止并返回该值。如果所有的表达式都是空值,最终将返回一个空值。使用COALESCE在于大部分包含空值的表达式最终将返回空值。 展开全文
COALESCE是一个函数, (expression_1, expression_2, ...,expression_n)依次参考各参数表达式,遇到非null值即停止并返回该值。如果所有的表达式都是空值,最终将返回一个空值。使用COALESCE在于大部分包含空值的表达式最终将返回空值。
信息
数据库
Mysql Oracle
返回类型
expression
参    数
expression
中文名
依次参考各参数
外文名
coalesce
coalesce基本信息
注意:连接操作符“||”是一个值得注意的例外。例如,空值加任何值都是空值,空值 乘任何值也都是空值,依此类推。expression任何类型的表达式。n表示可以指定多个表达式的占位符。所有表达式必须是相同类型,或者可以隐性转换为相同的类型。Mysql将相同的值作为 expression 返回。返回表达式中第一个非空表达式,如有以下语句:SELECT COALESCE(NULL,NULL,3,4,5) FROM dual其返回结果为:3如果所有自变量均为 NULL,则 COALESCE 返回 NULL 值。COALESCE(expression1,...n) 与此 CASE 函数等价:CASEWHEN (expression1 IS NOT NULL) THEN expression1...WHEN (expressionN IS NOT NULL) THEN expressionNELSE NULL
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  • COALESCE

    2019-08-06 14:41:55
    COALESCE 表达式是 CASE 表达式的语法快捷方式。 即查询优化器将代码COALESCE(expression1,…n) 重写为以下 CASE 表达式: SQL: CASE WHEN (expression1 IS NOT NULL) THEN expression1 WHEN (expression2 IS NOT ...

    COALESCE 表达式是 CASE 表达式的语法快捷方式。 即查询优化器将代码COALESCE(expression1,…n) 重写为以下 CASE 表达式:

    CASE  
    WHEN (expression1 IS NOT NULL) THEN expression1  
    WHEN (expression2 IS NOT NULL) THEN expression2  
    ...  
    ELSE expressionN  
    END  
    

    COALESCE(expression1,…n)

    SELECT Name, Class, Color, ProductNumber,  
    COALESCE(Class, Color, ProductNumber) AS FirstNotNull  
    FROM Production.Product; 
    

    COALESCE(Class, Color, ProductNumber) 按顺序找到第一个不为NULL的值

    展开全文
  • coalesce

    2017-03-13 22:38:50
    coalesce(expr1, expr2, ...) 参数说明:expri是要测试的值,所有这些值类型必须相同,或为null, 否则会引发异常。 返回值:返回值类型和参数类型相同。 备注:参数至少要有一个,否则返回异常。

    用途:返回列表中第一个非null的值,如果列表中所有的值都是null则返回null

    coalesce(expr1, expr2, ...)

    参数说明:expri是要测试的值,所有这些值类型必须相同,或为null, 否则会引发异常。

    返回值:返回值类型和参数类型相同。

    备注:参数至少要有一个,否则返回异常。

    展开全文
  • COALESCE

    2006-02-17 13:05:00
    COALESCE返回其参数中第一个非空表达式。语法COALESCE ( expression [ ,...n ] ) 参数expression任何类型的表达式。n表示可以指定多个表达式的占位符。所有表达式必须是相同类型,或者可以隐性转换为相同的类型。...

    COALESCE

    返回其参数中第一个非空表达式。

    语法

    COALESCE ( expression [ ,...n ] )

    参数

    expression

    任何类型的表达式。

    n

    表示可以指定多个表达式的占位符。所有表达式必须是相同类型,或者可以隐性转换为相同的类型。

    返回类型

    将相同的值作为 expression 返回。

    注释

    如果所有自变量均为 NULL,则 COALESCE 返回 NULL 值。

    COALESCE(expression1,...n) 与此 CASE 函数等价:

    CASE
       WHEN (expression1 IS NOT NULL) THEN expression1
       ...
       WHEN (expressionN IS NOT NULL) THEN expressionN
       ELSE NULL
    
    示例

    在下面的示例中,显示包含三列有关某个雇员每年工资收入信息的 wages 表:hourly_wage、salarycommission。但是,每个雇员只能接受一种付款方式。若要确定支付给所有雇员的工资总额,请使用 COALESCE 函数接受在 hourly_wage、salary commission 中找到的非空值。

    SET NOCOUNT ON
    GO
    USE master
    IF EXISTS (SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES 
          WHERE TABLE_NAME = 'wages')
       DROP TABLE wages
    GO
    CREATE TABLE wages
    (
       emp_id      tinyint    identity,
       hourly_wage   decimal   NULL,
       salary      decimal    NULL,
       commission   decimal   NULL,
       num_sales   tinyint   NULL
    )
    GO
    INSERT wages VALUES(10.00, NULL, NULL, NULL)
    INSERT wages VALUES(20.00, NULL, NULL, NULL)
    INSERT wages VALUES(30.00, NULL, NULL, NULL)
    INSERT wages VALUES(40.00, NULL, NULL, NULL)
    INSERT wages VALUES(NULL, 10000.00, NULL, NULL)
    INSERT wages VALUES(NULL, 20000.00, NULL, NULL)
    INSERT wages VALUES(NULL, 30000.00, NULL, NULL)
    INSERT wages VALUES(NULL, 40000.00, NULL, NULL)
    INSERT wages VALUES(NULL, NULL, 15000, 3)
    INSERT wages VALUES(NULL, NULL, 25000, 2)
    INSERT wages VALUES(NULL, NULL, 20000, 6)
    INSERT wages VALUES(NULL, NULL, 14000, 4)
    GO
    SET NOCOUNT OFF
    GO
    SELECT CAST(COALESCE(hourly_wage * 40 * 52, 
       salary, 
       commission * num_sales) AS money) AS 'Total Salary' 
    FROM wages
    GO
    

    下面是结果集:

    Total Salary 
    ------------ 
    20800.0000
    41600.0000
    62400.0000
    83200.0000
    10000.0000
    20000.0000
    30000.0000
    40000.0000
    45000.0000
    50000.0000
    120000.0000
    56000.0000
    
    (12 row(s) affected)
    
    展开全文
  • Coalesce concurrency

    2020-11-20 11:45:18
    That said - I had to stop the scheduling backups, remove all snapshots and let the system perform its coalesce, because for a 7TB VDIs, on a 20TB SR, I was getting out of space. It has been coalescing...
  • Building polygons Coalesce

    2020-11-29 00:20:10
    <p>I used --coalesce with --hilbert reordering. Several buildings have been merged but most of them are still separated, even if they looks like to be adjacent. It seems "coalesce" checks if ...
  • coalesce with falsy

    2020-11-23 08:53:54
    m finding myself using <code>coalesce</code> for achieving clean and idiomatic code. But sometimes my data providers return me objects, where some keys I pick <em>present, but <em>falsy</em> (<code>...
  • Implement COALESCE function

    2020-11-29 08:10:50
    <div><p>Here's what we get now: <pre><code>sql ...# select coalesce(id, value) as coal from a; function coalesce not found. </code></pre> <p>It seems that we already have the function type: ...
  • postgresql coalesce COALESCE

    千次阅读 2018-09-02 17:09:56
    https://www.postgresql.org/docs/10/static/functions-conditional.html#FUNCTIONS-COALESCE 9.17.2. COALESCE COALESCE(value [, ...]...The COALESCE function returns the first of its arguments that is not...

    https://www.postgresql.org/docs/10/static/functions-conditional.html#FUNCTIONS-COALESCE

    9.17.2. COALESCE

    COALESCE(value [, ...])

    The COALESCE function returns the first of its arguments that is not null. Null is returned only if all arguments are null. It is often used to substitute a default value for null values when data is retrieved for display, for example:

    SELECT COALESCE(description, short_description, '(none)') ...

    This returns description if it is not null, otherwise short_description if it is not null, otherwise (none).

    Like a CASE expression, COALESCE only evaluates the arguments that are needed to determine the result; that is, arguments to the right of the first non-null argument are not evaluated. This SQL-standard function provides capabilities similar to NVL and IFNULL, which are used in some other database systems.

    explame:

    select coalesce(null, 'test');
     coalesce 
    ----------
     test
    (1 row)
    
    select coalesce(null, 0);
     coalesce 
    ----------
            0
    (1 row)
    
    展开全文
  • coalesce-along-list

    2020-11-27 17:27:37
    Coalesce( ([Coalesce('user.client', default=SKIP)], T[0]), default=None)) </code></pre> <p>basically, you want to get the first element in a list which has a valid value here's...
  • <p>I am trying by a WHILE to show course name (workis fine) and by COALESCE to show in each course the course's subjects ID, this should be the final result: <p><strong>Curso de Programación ...
  • <div><p>I have some input (bit too large to add here), which results in missing features when I use reorder and coalesce. <p>I'm attaching the mbtiles of one tile that shows the problem (10/525/...
  • From my POV <code>Infection\Mutator\Operator\Coalesce</code> mutator is redundant when this PR is merged. Thoughts?</p><p>该提问来源于开源项目:infection/infection</p></div>
  • <pre><code>SELECT name, COALESCE(tb1.price, tb2.standardprice) as price, COALESCE(tb1.period, tb2.period) as period FROM table1 as tb1 LEFT JOIN table2 as tb2 ON (tb1.pk= tb2.fk) AND fk=1; </code></...
  • mysql COALESCE函数

    千次阅读 2018-10-31 11:28:32
    COALESCE(value,…)是一个可变参函数,可以使用多个参数。 作用:接受多个参数,返回第一个不为NULL的参数,如果所有参数都为NULL,此函数返回NULL;当它使用2个参数时,和IFNULL函数作用相同。 使用示例: ...
  • coalesce函数

    万次阅读 2019-06-24 15:07:24
    coalesce函数在Maxcompute里面的官方解释如下: 具体怎么用呢? 上面的函数说明通俗来说coalesce()的作用是:返回传入的参数中第一个非null的值。expre1不为空值则返回expre1;否则判断expre2是否是空值,如果...
  • SQL——coalesce函数详解

    万次阅读 多人点赞 2019-01-22 15:50:20
    最近写SQL的过程中,学习到一个非常有用的函数:coalesce。特别是在做统计的时候,这个函数作为条件可以兼顾到一些特殊情况。这里做一下总结和分享。 用途: (1):将控制替换成其他值; (2):返回第一个非空值...
  • <p>I'm trying to use COALESCE to deal with sql injections in Go. <pre><code>query := `SELECT mc.company_name_full, msc.company_id, msc.cdate, %s FROM %s AS mc INNER JOIN %s AS msc ON (mc.id = msc....
  • <div><p>Does the library support coalesce find requests? So lets say I need to find 3 <code>items</code> with ids: 1,2,3. <p>Instead of performing 3 api calls. It does it in one, passing the id as a ...
  • <pre><code> SELECT COALESCE(table1.*, table2.*) FROM table1 LEFT JOIN table2 USING(id) WHERE id = 4; </code></pre> <p>But in Table 2, may not have the record id "4"… <p>How can i get that result? ...
  • Coalesce rows

    2020-11-26 13:09:24
    <div><p>For #88 <p>/wip</p><p>该提问来源于开源项目:feast-dev/feast</p></div>

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