1. What is the use of CASCADE CONSTRAINTS?
When this clause is used with the DROP command, a parent table can be dropped even when a child table exists.
2. What are the different categories of SQL statements?
DDL, DML, DCL, Session Control, System Control.
3. What are the wildcards used for pattern matching?
Underscore (_) for single character substitution & % for multi-character substitution.
4. Why does the following command give a compilation error?
DROP TABLE &TABLE_NAME;
Variable names should start with an alphabet. Here the table name starts with ‘&' symbol. Any table name must start with alphabet. Table names starting with special characters are considered to be invalid hence give error.
5. How can I hide a particular table name of our schema?
You can hide the table name by creating synonyms.(e.g.) You can create a synonym y for table xcreate synonym y for x;
6. What is the parameter substitution symbol used with INSERT INTO command?
7. What will be the output of the following query?
SELECT REPLACE (TRANSLATE (LTRIM (RTRIM ('!!ATHEN!!','!'),'!'),'AN','**'),'*','TROUBLE') FROM DUAL;
8. Difference between VARCHAR and VARCHAR2?
Varchar means fixed length character data (size) i.e., min size-1 and max-2000.
Varchar2 means variable length character data i.e., min-1 to max-4000.
Varchar assigns total length to data. Suppose we have name , now with the case of if we entered NARINDER, totally 20 cells will be occupied. But in case of varchar2, 8 cells of memory coz there are 8 elements in that data.
9. What is the difference between DBMS and RDBMS?
1. RDBMS = DBMS + Referential Integrity2. An RDBMS is one that follows 12 rules of CODD.
10. When we give SELECT * FROM EMP; How does oracle respond?
When u give SELECT * FROM EMP; the server check all the data in the EMP file and it displays the data of the EMP file. When we give select * from emp it will shows the records of table emp if the table contain records. If it hasn't any records then it will shows no rows selected.