coalesce

spark04 join leftOuterjoin rightOuterJoin cogroup scala> var arr = Array(("zhangsan",200),("lisi",300),("wangwu",350)) arr: Array[(String, Int)] = Array((zhangsan,200), (lisi,300), (wangwu,350)) scala> var arr1 = Array(("zhangsan",10),("lisi",15),("zhaosi",20)) arr1: Array[(String, Int)] = Array((zhangsan,10), (lisi,15), (zhaosi,20)) scala> sc.makeRDD(arr,3) res0: org.apache.spark.rdd.RDD[(String, Int)] = ParallelCollectionRDD[0] at makeRDD at <console>:27 scala> sc.makeRDD(arr1,3) res1: org.apache.spark.rdd.RDD[(String, Int)] = ParallelCollectionRDD[1] at makeRDD at <console>:27 scala> scala>

COALESCE()函数 主流数据库系统都支持COALESCE()函数，这个函数主要用来进行空值处理，其参数格式如下： COALESCE ( expression,value1,value2……,valuen) COALESCE()函数的第一个参数expression为待检测的表达式，而其后的参数个数不定。 COALESCE()函数将会返回包括expression在内的所有参数中的第一个非空表达式。 如果expression不为空值则返回expression；否则判断value1是否是空值， 如果value1不为空值则返回value1；否则判断value2是否是空值， 如果value2不为空值则返回value2；……以此类推， 如果所有的表达式都为空值，则返回NULL。 我们将使用COALESCE()函数完成下面的功能，返回人员的“重要日期”： 如果出生日期不为空则将出生日期做为“重要日期”，如果出生日期为空则判断注册日期是否为空，如果注册日期不为空则将注册日期做为“重要日期”，如果注册日期也为空则将“2008年8月8日”做为“重要日期”。实现此功能的SQL语句如下： MYSQL、MSSQLServer、DB2: SELECT FName,FBirthDay,FRegDay, COALESCE(FBirthDay,FRegDay, '2008-08-08') AS

with t1 as ( select NUll as col1, '' as col2, 'aaa' as col3 ) --关于COALESCE用法 当col1 为 null时候返回 col2 依次类推 当col2 为 null时 返回col3 --很多朋友会以为这里返回col3 其实不是。那么怎么才能返回想要的结果col3, 搭配nullif函数即可 --select COALESCE(col1, col2, col3) from t1 select COALESCE(nullif(col1,''), nullif(col2,''), nullif(col3,'')) from t1 　　 来源： https://www.cnblogs.com/adsoft/p/11526872.html

I have the following namedQuery select new test.entity.Emp(COALESCE(k.projectId,'N') as projectId, k.projectName) from Emp o inner join o.projects k However I am getting error expecting RIGHT_ROUND_BRACKET, found '(' How to handle COALESCE in namedQuery? Are there any other ways to handle null values in JPA? gknicker Coalesce is supported by JPA 2.0 API . The new construct is proprietary to Hibernate, not necessarily supported in all JPA implementations. First try the query without also trying to construct an object: select COALESCE(k.projectId,'N') as projectId, k.projectName from Emp o inner

Say I have the following table: TABLE: product =============================================================================== | product_id | language_id | name | description | =============================================================================== | 1 | 1 | Widget 1 | Really nice widget. Buy it now! | ------------------------------------------------------------------------------- | 1 | 2 | Lorem 1 | | ------------------------------------------------------------------------------- How do I query this such that it tries to give me the name and description where language_id = 2, but fall

coalesce重新分区，可以选择是否进行shuffle过程。由参数shuffle: Boolean = false/true决定 repartition实际上是调用的coalesce，默认是进行shuffle的 来源： https://www.cnblogs.com/xiangyuguan/p/11456753.html

I have a number of functions: String first(){} String second(){} ... String default(){} Each can return a null value, except the default. each function can take different parameters. For example, first could take no arguments, second could take in a String, third could take three arguments, etc. What I'd like to do is something like: ObjectUtils.firstNonNull(first(), second(), ..., default()); The problem is that because of the function call, this does eager evaluation. Where'd I'd like to exit early, say after the second function (because the function calls can be expensive, think API calls,

I need to fill a cell with the first non-empty entry in a set of columns (from left to right) in the same row - similar to coalesce() in SQL. In the following example sheet --------------------------------------- | | A | B | C | D | --------------------------------------- | 1 | | x | y | z | --------------------------------------- | 2 | | | y | | --------------------------------------- | 3 | | | | z | --------------------------------------- I want to put a cell function in each cell of row A such that I will get: --------------------------------------- | | A | B | C | D | ---------------------