How to Insert Union Tables to Table In Postgresql?

To insert union tables to a table in PostgreSQL, you can first create a view that combines the data from multiple tables using the UNION operator. This view will act as a virtual table that represents the combined data of the underlying tables.

To create a view that includes the union of tables, you can use a SQL query like the following:

1
2
3
4
5
6

CREATE VIEW combined_data AS
SELECT column1, column2, ...
FROM table1
UNION
SELECT column1, column2, ...
FROM table2;

Once you have created the view, you can then insert data into it as if it were a regular table. The data will be stored in the underlying tables that were used in the union query.

To insert data into the view, you can use a standard INSERT statement like this:

1
2

INSERT INTO combined_data (column1, column2, ...)
VALUES (value1, value2, ...);

This will insert the data into the appropriate underlying tables based on the structure of the view and the union query. Remember that views are virtual tables and do not store data themselves, so any changes made to the view will affect the underlying tables.

How to use the UNION keyword in PostgreSQL?

In PostgreSQL, the UNION keyword is used to combine the results of two or more SELECT statements into a single result set. Here's how you can use the UNION keyword:

1. Write your first SELECT statement and specify the columns you want to select and any conditions or filters you want to apply.

1
2
3

SELECT column1, column2
FROM table1
WHERE condition1;

1. Use the UNION keyword to combine the results of the first SELECT statement with the results of a second SELECT statement. Make sure the second SELECT statement selects the same number of columns as the first SELECT statement.

1
2
3
4
5
6
7

SELECT column3, column4
FROM table2
WHERE condition2
UNION
SELECT column5, column6
FROM table3
WHERE condition3;

1. You can chain multiple SELECT statements together using the UNION keyword to combine their results into a single result set.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11

SELECT column1, column2
FROM table1
WHERE condition1
UNION
SELECT column3, column4
FROM table2
WHERE condition2
UNION
SELECT column5, column6
FROM table3
WHERE condition3;

1. By default, the UNION keyword removes duplicate rows from the result set. If you want to include duplicate rows, you can use the UNION ALL keyword instead.

1
2
3
4
5
6
7

SELECT column1, column2
FROM table1
WHERE condition1
UNION ALL
SELECT column3, column4
FROM table2
WHERE condition2;

1. You can also use the ORDER BY clause to sort the result set returned by the UNION keyword.

1
2
3
4
5
6
7
8

(SELECT column1, column2
 FROM table1
 WHERE condition1)
UNION
(SELECT column3, column4
 FROM table2
 WHERE condition2)
ORDER BY column1;

This is how you can use the UNION keyword in PostgreSQL to combine the results of multiple SELECT statements into a single result set.

How to insert data from multiple tables into one table in PostgreSQL?

You can insert data from multiple tables into one table in PostgreSQL using the INSERT INTO...SELECT statement.

Here's an example:

1
2
3
4
5

INSERT INTO destination_table (column1, column2, column3)
SELECT t1.column1, t2.column2, t3.column3
FROM source_table1 t1
JOIN source_table2 t2 ON t1.common_column = t2.common_column
JOIN source_table3 t3 ON t1.common_column = t3.common_column;

In this example, we are inserting data from three different source tables (source_table1, source_table2, source_table3) into one destination table (destination_table). We are selecting specific columns from each source table and joining them on a common column.

Make sure that the columns you are selecting match the data types of the columns in the destination table, and that the common column on which you are joining the tables exists in all source tables.

How to include only distinct values in a union query in PostgreSQL?

To include only distinct values in a UNION query in PostgreSQL, you can use the keyword "UNION DISTINCT" instead of just "UNION".

Here is an example query:

1
2
3

SELECT column1 FROM table1
UNION DISTINCT
SELECT column2 FROM table2;

By using "UNION DISTINCT", PostgreSQL will remove any duplicate values that appear in the result set.

What is the function of the UNION operator in PostgreSQL?

The UNION operator in PostgreSQL is used to combine the result sets of two or more SELECT statements into a single result set. The UNION operator removes duplicate rows from the combined result set. This allows you to easily merge data from multiple tables or queries that have compatible column data types.

What is PostgreSQL?

PostgreSQL is an advanced open-source relational database management system (RDBMS) known for its stability, scalability, and extensibility. It is a powerful database system that supports various features such as ACID compliance, transactions, foreign keys, triggers, and stored procedures. PostgreSQL is widely used in web applications, mobile apps, and data warehousing applications.