并且公司主表中的(ID)与子表中的(BelongID)建立关联,即主外键关系; 一个公司对应着多个客户,即ID:BelongID = 1 : n关系.主表的ID为自动生成编号.
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一个删除操作可以从一个父表中删除一条记录，使得相关子表中的记录在父表中没有与之匹配的记录。
A delete operation could remove a record from a parent table, leaving records in an associated child table that no longer have a matching record in the parent table.
一个更新操作可改变父表中的一条记录，使得相关子表中的记录在父表中没有与之匹配的记录。
An update operation could change a record in a parent table, leaving records in an associated child table that no longer have a matching record in the parent table.
索引号与电子表格中当前单元格的列号相同。
The index number is the same as the current cell's column number in the spreadsheet.
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