You can disable integrity constraints temporarily so that large amounts of data can be loaded without the overhead of constraint checking. Which of the following is true of a variable character data type? dictionary. The following image shows the Customers and Orders tables. You can control what concurrency mechanisms are used to maintain these relationships, and, depending on the situation, this can be highly beneficial. The table currently exists as illustrated in Figure 25-10. "Deferred Constraint Checking". When referenced data is updated or deleted, all associated dependent data is set to a default value. For example, if EMPNO references MGR in the TMP table, then deleting a manager causes the rows for all employees working for that manager to have their MGR value set to null. Oracle also allows you to enforce integrity rules with a nondeclarative approach using database triggers (stored database procedures automatically invoked on insert, update, or delete operations). Inserts, updates, and deletes on the parent table do not require any locks on the child table, although updates and deletes will wait for row-level locks on the indexes of the child table to clear. For example, if a primary key value is referenced by a value in the foreign key, then the referenced primary key value cannot be deleted because of the dependent data. Referential integrity is a database concept that ensures Consequently, since the foreign key constraint included the ‘ON DELETE CASCADE’ command, SQL Server automatically removes linked child records when the parent record is deleted from the Customers table. For example, if we delete record number 15 in a primary table, we need to be sure that there’s no foreign key in any related table with the value of 15. (Oracle uses No Action as its default action.). Inserts into the parent table do not require any locks on the child table. INSERT, UPDATE, and DELETE statements on the child table do not acquire any locks on the parent table, although INSERT and UPDATE statements will wait for a row-lock on the index of the parent table to clear. If the foreign key specifies ON DELETE CASCADE, then the DELETE statement results in a table-level share-subexclusive lock on the child table. Notice that a share lock of the entire child table is required until the transaction containing the DELETE statement for the parent table is committed. Different tables in a relational database can be related by common columns, and the rules that govern the relationship of the columns must be maintained. Which of the following shows how you would begin to make a table in SQL? A referential integrity constraint requires that for each row of a table, the value in the foreign key matches a value in a parent key. Oracle enforces all PRIMARY KEY constraints using indexes. it show referance to another location with accuracy. When coded in a WHERE clause, which of the following search conditions will not return a result set that includes all invoices with an InvoiceTotal value of $1000 or less?