How to Combine 2 Select Statements In Oracle?

To combine two SELECT statements in Oracle, you can use the UNION operator. The UNION operator is used to combine the result sets of two or more SELECT statements into a single result set. This allows you to retrieve data from multiple tables or views in a single query.

To use the UNION operator, simply write your first SELECT statement, followed by the keyword UNION, and then write your second SELECT statement. Make sure that both SELECT statements have the same number of columns and that the data types of the corresponding columns match.

For example: SELECT column1, column2 FROM table1 UNION SELECT column1, column2 FROM table2;

This query will combine the result sets of the two SELECT statements and return a single result set. You can also use the UNION ALL operator if you want to include duplicate rows in the result set.

Overall, the UNION operator is a useful tool for combining multiple SELECT statements in Oracle to gather data from different sources in a single query.

How to combine 2 select statements in Oracle with a SUM function?

You can combine 2 SELECT statements in Oracle with a SUM function by using a UNION ALL to combine the results of the two queries and then applying the SUM function to calculate the sum of the combined results. Here is an example:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10

SELECT SUM(total_sales) AS combined_sales
FROM (
  SELECT SUM(sales_amount) AS total_sales
  FROM sales_table_1
  WHERE year = 2021
  UNION ALL
  SELECT SUM(sales_amount) AS total_sales
  FROM sales_table_2
  WHERE year = 2021
);

In this example, we are calculating the total sales amount from two different sales tables for the year 2021 and combining the results using UNION ALL before applying the SUM function to calculate the sum of the combined sales.

How to combine 2 select statements in Oracle with a subquery?

To combine 2 select statements in Oracle with a subquery, you can use the UNION clause. Here is an example:

1
2
3
4
5
6
7

SELECT column1, column2
FROM table1
WHERE column3 IN (SELECT column4 FROM table2)
UNION
SELECT column5, column6
FROM table3
WHERE column7 = (SELECT column8 FROM table4);

In this example, the first SELECT statement retrieves data from table1 where the value in column3 is present in the results of the subquery selecting data from table2. The second SELECT statement retrieves data from table3 where the value in column7 is equal to the result of the subquery selecting data from table4. The results of both SELECT statements are combined using the UNION clause.

How to combine 2 select statements in Oracle with a UNION vs UNION ALL comparison?

To combine two SELECT statements in Oracle using UNION or UNION ALL, you can use the following syntax:

1. UNION: This operator is used to combine the result sets of two queries and remove any duplicate rows.

Syntax:

1
2
3
4
5
6
7

SELECT column1, column2
FROM table1
WHERE condition
UNION
SELECT column1, column2
FROM table2
WHERE condition;

Example:

1
2
3
4
5

SELECT first_name, last_name
FROM employees
UNION
SELECT first_name, last_name
FROM contractors;

1. UNION ALL: This operator is used to combine the result sets of two queries, including duplicate rows.

Syntax:

1
2
3
4
5
6
7

SELECT column1, column2
FROM table1
WHERE condition
UNION ALL
SELECT column1, column2
FROM table2
WHERE condition;

Example:

1
2
3
4
5

SELECT first_name, last_name
FROM employees
UNION ALL
SELECT first_name, last_name
FROM contractors;

In summary, if you want to include duplicate rows in your result set, you should use UNION ALL. If you want to remove duplicate rows, you should use UNION.