Original subtitles

0 Next, we are going to discuss the union operator. 1

Union operator combines the result sets of two or more select statement. 2

So in except we saw that it is giving us the ResultSet of one table, and from that it removed 3

the result set of other table. union is combining both of these ResultSet and while combining 4

the duplicate rows from both, the result sets will be removed. 5

So it will be similar to the select distinct. 6

So the syntax for this union operators, you select the expressions that you want from table one, you 7

can specify where conditions also. 8

Then you write union, just like we wrote, except then you specify the second select condition with expressions. 9

One thing to note here is for expression 1 in the first statement and expression 1 in the second 10

statement. 11

These two should have the same data types if expression, one in first selected statement is integer then it should be 12

integer 13

in the second select statement also and the number of expressions in the first select statement, if it is n 14

here, it should be. 15

n in the second select statement also. you can specify more than two select statements using multiple 16

unions. 17

Let us look at an example. 18

Suppose you want to find out all the customer ideas that you have in your database, either they are 19

present in the sales table or they are present in the customer table. 20

To do that, to get that combined customer ID table, we will use the union operator will write select customer 21

Id from sales table. 22

And Union select customer id from customer table, and we will order this by the customer id. 23

Let's go right this so select customer id from sales table 24

union select customer id from customer table 25

order by customer Id. 26

Just compare that this is exactly same as the except query that we wrote just that except it replaced 27

by Union. Let us run this query 28

You can see 10315, which is not president in the customer table is present in our ResultSet, 29

10375 is part of both. 30

And it is President in the ResultSet, 10480 which is not part of sales table, is present in this result set 31

So basically, all the customer ids are present in our result set. This is how we use union and this completes the 32

joins and other table combination operators.