Hive,coalesce用法

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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。

hive> select coalesce(1,2);
OK
1
Time taken: 0.23 seconds, Fetched: 1 row(s)

hive> select coalesce(null,2);
OK
2
Time taken: 0.079 seconds, Fetched: 1 row(s)

hive> select coalesce(null,null,3);
OK
3
Time taken: 0.11 seconds, Fetched: 1 row(s)

hive> select coalesce(null,2,3);
OK
2
Time taken: 0.055 seconds, Fetched: 1 row(s)

hive> select coalesce(null,null);
OK
NULL
Time taken: 1.002 seconds, Fetched: 1 row(s)

end