MIS 325 Lecture Notes - Lecture 11: Unique Key, Data Type, Database

• School: UT-Austin
• Department: Management Information Systems
• Course: MIS 325
• Professor: Ayvaci

Document Summary

Novalidate: enables constraint for new values only. Rename table_name to new_table_name: renames an existing table. Truncate table: deletes all data from a table without deleting the definition for the table. Drop table: deletes table from the current database/schema entirely. You can"t drop or truncate a table if a foreign key constraint in another table refers to that table. Speeds up joins and searches by providing a way for a dbms to go directly to a row rather than having to search through all the rows. Primary keys and unique constraints have indexes created by default. In addition, you may want to create indexes for foreign keys and other columns that are used frequently in search conditions or joins. Avoid creating indexes on columns that are updated frequently. Function-based index: an index that"s based on an expression. Create index index_ix on table_name (column desc) A database object that automatically generates a sequence of integer values.