Answer / soubhagya

Union:
It retrieves only distinct records.

Union all:
This retrieves duplicate records too.

but in performance issue
unioun all is better becoz it doesnot sort, filter the
record so its faster.

Answer / srinivas

Another difference is that union will sort the result sets
whereas union all will not.

Answer / vibha kant pandey

Hi friends check it this may help you all.

UNION
The UNION command is used to select related information from
two tables, much like the JOIN command. However, when using
the UNION command all selected columns need to be of the
same data type. With UNION, only distinct values are selected.

UNION ALL
The UNION ALL command is equal to the UNION command, except
that UNION ALL selects all values.

The difference between Union and Union all is that Union all
will not eliminate duplicate rows, instead it just pulls all
rows from all tables fitting your query specifics and
combines them into a table.

A UNION statement effectively does a SELECT DISTINCT on the
results set. If you know that all the records returned are
unique from your union, use UNION ALL instead, it gives
faster results.

Example :-
Table X contain values(a,b,c) and Table Y
contain values(c,d,e)
In Case Of Union we will get Result-a,b,c,d,e
and other hand (Union All ) we will get-a,b,c,c,d,e.

Answer / leena

union all will combine the outputs of two or more queries.
union will combine the outputs of two or more queries but remove or ignore duplicate value in output.
union all is most faster as compare to union

Can we use insert statement in function?

0 Answers  

---

Types of cursors and explanation each of them ?

4 Answers   DELL,

---

What are the benefits of pl/sql packages?

0 Answers  

---

What are different types of sql commands?

0 Answers  

---

How do you declare a constant?

0 Answers  

---

i have a customer table. trans_id trans_date trans_amt debit_credit_indicator 001 01-JAN-13 1099 cr 001 12-JAN-13 500 db 002 24-FEB-13 400 db 002 23-MAR-13 345 cr 001 18-APR-13 800 cr 002 15-MAR-13 600 db 001 12-FEB-13 200 cr i want like this output. trans_id trans_amt debit_credit_indicator i want get highest credit amount and lowest credit amount and highest debit amount and lowest debit amount for each trans_id.

2 Answers   Oracle,

---

Write a procedure to return the month and the number of developers joined in each month (cursor )

2 Answers   Tech Mahindra,

---

What is pl/sql tables?

7 Answers   TCS,

---

How would you pass hints to the sql processor?

0 Answers  

---

i have table T!. A B C D NULL 1 2 3 4 NULL 5 6 7 8 NULL 9 10 11 12 NULL. I WANT COUNT OF NULL VALUES IN TABLE. WRITE A QUERY.

14 Answers   iGate, Wipro,

---

what are the different tables present in mysql, which type of table is generated when we are creating a table in the following syntax: create table employee (eno int(2),ename varchar(10)) ? : Sql dba

0 Answers  

---

What are the methods of filing?

0 Answers  

---