MAPREDUCE服务 MRS-JOINS:Qualifying Column Names

时间:2024-11-06 14:23:39

Qualifying Column Names

当JOIN的两个relation有相同的列名时,列引用必须使用relation别名(如果relation有别名)或relation名称进行限定:

SELECT nation.name, region.name FROM nation CROSS JOIN region;
SELECT n.name, r.name FROM nation AS n CROSS JOIN region AS r;
SELECT n.name, r.name FROM nation n CROSS JOIN region r;
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