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请各个高手帮译完下面这段，谢谢！
Using Relational Rules to Prevent Accidental Deletion： Many DBMSs allow you to enforce rules that prevent the dropping of tables that are related to other tables. When these rules are enforced, if you issue a DROP TABLE statement against a table that is part of a relationship, the DBMS blocks the operation until the relationship was removed. It is a good idea to enable these options, if available, to prevent the accidental dropping of needed tables.
Renaming Tables
Table renaming is supported differently by each DBMS. There is no hard and fast standard for this operation. DB2, MySQL, Oracle, and PostgreSQL users can use the RENAME statement. SQL Server and Sybase users can use the supplied sp_rename stored procedure.
The basic syntax for all rename operations requires that you specify the old name and a new name. However, there are DBMS implementation differences. Refer to your own DBMSdo
cumentation for details on supported syntax.
Summary
In this lesson, you learned several new SQL statements. CREATE TABLE is used to create new tables, ALTER TABLE is used to change table columns (or other objects like constraints or indexes), and DROP TABLE is used to completely delete a table. These statements should be used with extreme caution, and only after backups have been made. As the exact syntax of each of these statements varies from one DBMS to another, you should consult your own DBMSdo
cumentation for more information.
Using Relational Rules to Prevent Accidental Deletion： Many DBMSs allow you to enforce rules that prevent the dropping of tables that are related to other tables. When these rules are enforced, if you issue a DROP TABLE statement against a table that is part of a relationship, the DBMS blocks the operation until the relationship was removed. It is a good idea to enable these options, if available, to prevent the accidental dropping of needed tables.
Renaming Tables
Table renaming is supported differently by each DBMS. There is no hard and fast standard for this operation. DB2, MySQL, Oracle, and PostgreSQL users can use the RENAME statement. SQL Server and Sybase users can use the supplied sp_rename stored procedure.
The basic syntax for all rename operations requires that you specify the old name and a new name. However, there are DBMS implementation differences. Refer to your own DBMSdo
cumentation for details on supported syntax.
Summary
In this lesson, you learned several new SQL statements. CREATE TABLE is used to create new tables, ALTER TABLE is used to change table columns (or other objects like constraints or indexes), and DROP TABLE is used to completely delete a table. These statements should be used with extreme caution, and only after backups have been made. As the exact syntax of each of these statements varies from one DBMS to another, you should consult your own DBMSdo
cumentation for more information.
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