There is a string ‘120000 12 0 .125′ ,how you will find the position of the decimal place
INSTR(’120000 12 0 .125′,1,’.') output 13
There is a ‘%’ sign in one field of a column. What will be the query to find it.
‘\’ Should be used before ‘%’.
When you use WHERE clause and when you use HAVING clause
HAVING clause is used when you want to specify a condition for a group function and it is written after GROUP BY clause The WHERE clause is used when you want to specify a condition for columns, single row functions except group functions and it is written before GROUP BY clause if it is used.
Which is more faster - IN or EXISTS
EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.
What is a OUTER JOIN
Outer Join–Its a join condition used where you can query all the rows of one of the tables in the join condition even though they dont satisfy the join condition.
How you will avoid your query from using indexes
SELECT * FROM emp Where emp_no+’ ‘=12345; i.e you have to concatenate the column name with space within codes in the where condition. SELECT /*+ FULL(a) */ ename, emp_no from emp where emp_no=1234; i.e using HINTS
What is a pseudo column. Give some examples
It is a column that is not an actual column in the table. eg USER, UID, SYSDATE, ROWNUM, ROWID, NULL, AND LEVEL. Suppose customer table is there having different columns like customer no, payments.What will be the query to select top three max payments. SELECT customer_no, payments from customer C1 WHERE 3<=(SELECT COUNT(*) from customer C2 WHERE C1.payment <= C2.payment)
What is the purpose of a cluster.
Oracle does not allow a user to specifically locate tables, since that is a part of the function of the RDBMS. However, for the purpose of increasing performance, oracle allows a developer to create a CLUSTER. A CLUSTER provides a means for storing data from different tables together for faster retrieval than if the table placement were left to the RDBMS.
What is a cursor.
Oracle uses work area to execute SQL statements and store processing information PL/SQL construct called a cursor lets you name a work area and access its stored information A cursor is a mechanism used to fetch more than one row in a Pl/SQl block.
Difference between an implicit & an explicit cursor.
PL/SQL declares a cursor implicitly for all SQL data manipulation statements, including quries that return only one row. However,queries that return more than one row you must declare an explicit cursor or use a cursor FOR loop.
Explicit cursor is a cursor in which the cursor name is explicitly assigned to a SELECT statement via the CURSOR…IS statement. An implicit cursor is used for all SQL statements Declare, Open, Fetch, Close. An explicit cursors are used to process multirow SELECT statements An implicit cursor is used to process INSERT, UPDATE, DELETE and single row SELECT. .INTO statements.
What are cursor attributes
%ROWCOUNT
%NOTFOUND
%FOUND
%ISOPEN
What is a cursor for loop.
Cursor For Loop is a loop where oracle implicitly declares a loop variable, the loop index that of the same record type as the cursor’s record.
Difference between NO DATA FOUND and %NOTFOUND
NO DATA FOUND is an exception raised only for the SELECT….INTO statements when the where clause of the querydoes not match any rows. When the where clause of the explicit cursor does not match any rows the %NOTFOUND attribute is set to TRUE instead.
What a SELECT FOR UPDATE cursor represent.
SELECT……FROM……FOR……UPDATE[OF column-reference][NOWAIT] The processing done in a fetch loop modifies the rows that have been retrieved by the cursor. A convenient way of modifying the rows is done by a method with two parts: the FOR UPDATE clause in the cursor declaration, WHERE CURRENT OF CLAUSE in an UPDATE or declaration statement.
