external_table()external_table()
按名称引用外部表。References an external table by name.
external_table('StormEvent')
备注
external_table
函数与 table 函数具有类似的限制。Theexternal_table
function has similar restrictions as the table function.- 标准查询限制还适用于外部表查询。Standard query limits apply to external table queries as well.
语法Syntax
external_table
(
TableName [,
MappingName ] )
external_table
(
TableName [,
MappingName ] )
参数Arguments
TableName:正在查询的外部表的名称。TableName : The name of the external table being queried. 必须是引用
blob
、adl
或sql
类型的外部表的字符串文本。Must be a string literal referencing an external table of kindblob
,adl
orsql
.MappingName :映射对象的可选名称,该对象将实际(外部)数据分片中的字段映射到此函数输出的列。MappingName : An optional name of the mapping object that maps the fields in the actual (external) data shards to the columns output by this function.