State one similarity and difference between WHERE Clause and HAVING Clause?

Correct Answer: Use the DBMS_OUTPUT package Another possible method is to use the SHOW ERROR command

Correct Answer: By use of %ISOPEN status variable

Correct Answer: Cursor_Already_Open, Invalid_Cursor

Correct Answer: Too_many_rows No_Data_Found Zero_Error

Correct Answer: PL/SQL tables are scalar arrays that can be referenced by a binary digit They can be used to store values for later queries and calculations

Correct Answer: A default is a value which will be used by a column, if no value is supplied to that column while inserting data Yes, IDENTITY and TIMESTAMP columns are free from the bounds of default

Correct Answer: Constraints enable the RDBMS to enforce the integrity of the database automatically, without the need to create triggers, rule or defaults Types of Constraints: NOT NULL, CHEQUE, UNIQUE, PRIMARY KEY, FOREIGN KEY

Correct Answer: By default, primary key creates a clustered index on the column, whereas a unique key creates a non clustered index by default

Correct Answer: - A clustered index is a special type of index that reorders the way records in the table are physically stored Therefore table can have only one clustered index The leaf nodes of a clustered index contain the data pages - A non clustered index is a special type of index in which the logical order of the index does not match the physical stored order of the rows on disk The leaf node of a non clustered index does not consist of the data pages Instead, the leaf nodes contain index rows

Correct Answer: Delete command removes the rows from a table based on the condition that we provide with a WHERE clause Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command TRUNCATE: - TRUNCATE is faster and uses fewer system and transaction log resources than DELETE - TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log - TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains The counter used by an identity for new rows is reset to the seed for the column - You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint Because TRUNCATE TABLE is not logged, it cannot activate a trigger - TRUNCATE cannot be rolled back - TRUNCATE is DDL Command - TRUNCATE Resets identity of the table DELETE: - DELETE removes rows one at a time and records an entry in the transaction log for each deleted row - If you want to retain the identity counter, use DELETE instead If you want to remove table definition and its data, use the DROP TABLE statement - DELETE Can be used with or without a WHERE clause - DELETE Activates Triggers - DELETE can be rolled back - DELETE is DML Command - DELETE does not reset identity of the table Note: DELETE and TRUNCATE both can be rolled back when surrounded by TRANSACTION if the current session is not closed If TRUNCATE is written in Query Editor surrounded by TRANSACTION and if session is closed, it can not be rolled back but DELETE can be rolled back