Oracle subquery, create and manage tables, and oracle query Creation
SummarySubquery:
Single Row subquery: returns a single row
Use Single Row comparison Operators
Multi-row subquery: multi-row subquery returns multiple rows
Multiline operators:
IN, ANY, ALL
If the query result of the subquery is null, no rows are returned.
Create and manage tables:
Query Data Dictionary:
View a user-defined table:
SELECT table_nameFROM user_tables;
View user-defined data objects:
SELECT distinct object_typeFROM user_objects;
View user-defined tables, views, synonyms, and Sequences
SELECT * FROM user_catalog;
CREATE table
Two methods:
ALTER table
Rename a table:
RENAME dept TO detail_dept;
Table renamed.
Delete table:
Drop table dept80;
Table dropped.
Clear table:
Truncate table detail_dept;
Table truncated.
These DDL languages cannot be rolled back and are automatically submitted.
You need to practice more to become familiar and proficient.