数据项类型 meaning in English

data item type

When a data source contains multiple data item types , the data member specifies which data item type to use
当数据源包含多个数据项类型时，数据成员指定使用哪个数据项类型。
A join operation on two relations which share a common data item type produces a combined relation with attributes specified in the join operation
对共享一个公共数据项类型的两种关系，连接操作产生一种复合的关系，该关系具有连接操作中规定的属性。