In general, that data would live in a child table with a foreign key relation to the table contacts.
通常，那些数据应该存放在一张子表中，子表的外部关键字关联到表contacts。
When creating a foreign key, Informix automatically creates a B-Tree index on the child table when creating a foreign key.
创建一个外键时，Informix自动地在子表上创建一个B-Tree索引。
An update operation could change a record in a child table such that it no longer has a matching record in the associated parent table.
一个更新操作可改变子表中的一条记录，这样相关父表中不再有一条匹配的记录。
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.
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。
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 Foreign key constraint allows you to define referential integrity between a parent and child table.
外键约束允许您定义父表和子表之间的引用完整性。
Specifies the expression based on fields in the parent table that relates to an index in the child table.
指定基于父表中的字段而又与子表中的索引相关的表达式。
Shows how to ensure the selected row of a child table does not change, when a change is made to a field of the parent table.
演示如何确保在更改父表的字段时，子表的选定行不会发生改变。
Specifies if the record pointer remains on the same parent record until the record pointer of the child table moves through all related records.
指定是否只有在子表的记录指针遍历了所有相关记录之后，才移动父记录的记录指针。
To illustrate this, compare it to the predicate that is applied to the index scan numbered 5 in the plan, which is on the one and only column of the index on the child table.
为了展示这一点，将它与计划中第5号索引扫描上使用的谓词相比较，它针对子表中惟一的索引列。
To illustrate this, compare it to the predicate that is applied to the index scan numbered 5 in the plan, which is on the one and only column of the index on the child table.
为了展示这一点，将它与计划中第5号索引扫描上使用的谓词相比较，它针对子表中惟一的索引列。
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