How to Select 2 Tables In Oracle?

To select data from two tables in Oracle, you can use a SQL query with a JOIN clause. The JOIN clause allows you to combine rows from two or more tables based on a related column between them. You can specify the type of join, such as INNER JOIN, LEFT JOIN, RIGHT JOIN, or FULL JOIN, depending on the relationship you want between the tables. Additionally, you can use a WHERE clause to specify any additional conditions for retrieving data from the tables. By using a JOIN and WHERE clause in your SQL query, you can effectively select data from multiple tables in Oracle.

How to format the output of selecting 2 tables in Oracle using the TO_CHAR function?

To format the output of selecting 2 tables in Oracle using the TO_CHAR function, you can use the following syntax:

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SELECT TO_CHAR(table1.column_name, 'format_mask') AS alias_name1, TO_CHAR(table2.column_name, 'format_mask') AS alias_name2
FROM table1, table2
WHERE table1.column_name = table2.column_name;

In this query:

1. Replace table1 and table2 with the actual names of the tables you are selecting from.
2. Replace column_name with the actual names of the columns you want to select and format using the TO_CHAR function.
3. Replace 'format_mask' with the desired format mask for each column. You can use standard format masks for dates, numbers, or custom formats.
4. Use AS alias_name to give a custom name to the formatted columns in the output.

This query will select and format the specified columns from both tables and display the output with the specified format.

How to combine data from 2 tables in Oracle using a union operator?

To combine data from 2 tables in Oracle using a union operator, you can use the following SQL query:

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

In this query:

• Replace column1, column2, table1, and table2 with the actual column names and table names that you want to combine.
• The UNION operator is used to combine the results of the two SELECT statements into a single result set.
• Note that the columns selected in both SELECT statements must have the same data types and be in the same order.

After running this query, you will get a combined result set containing the data from both tables with duplicate rows removed. If you want to include duplicate rows, you can use the UNION ALL operator instead of UNION.

How to sort the results of selecting 2 tables in Oracle?

To sort the results of selecting two tables in Oracle, you can use the ORDER BY clause in your SQL query.

Here's an example query that selects data from two tables and sorts the results based on a specific column:

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SELECT table1.column1, table2.column2 
FROM table1 
JOIN table2 ON table1.join_column = table2.join_column 
ORDER BY table1.column1 ASC, table2.column2 DESC;

In this query, we are selecting data from two tables (table1 and table2) and using the JOIN keyword to join the two tables on a common column (join_column). The ORDER BY clause is then used to sort the results based on the column1 from table1 in ascending order and the column2 from table2 in descending order.

You can adjust the columns and sorting order based on your specific requirements.

What is the difference between inner join and outer join in Oracle?

In Oracle, an inner join returns only the rows that have matching values in both tables being joined. It only includes the rows that have a match in both tables.

On the other hand, an outer join returns all the rows from one table, along with the matching rows from the other table (if available). There are three types of outer joins in Oracle: left outer join, right outer join, and full outer join.

• Left outer join: Returns all the rows from the left table along with the matching rows from the right table.
• Right outer join: Returns all the rows from the right table along with the matching rows from the left table.
• Full outer join: Returns all the rows when there is a match in either the left or right table.

In summary, the main difference between inner join and outer join in Oracle is that an inner join returns only the matching rows, while an outer join returns all rows from at least one of the tables.

How can you merge data from 2 tables in Oracle?

There are several ways to merge data from two tables in Oracle, including using JOIN statements, subqueries, and the MERGE statement.

1. JOIN statement: You can use different types of JOIN statements such as INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN to combine data from two tables based on a common column or key. For example:

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SELECT table1.column1, table1.column2, table2.column3
FROM table1
JOIN table2 ON table1.common_column = table2.common_column;

1. Subquery: You can use a subquery to combine data from two tables. For example:

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SELECT column1, column2, (
    SELECT column3
    FROM table2
    WHERE table1.common_column = table2.common_column
)
FROM table1;

1. MERGE statement: The MERGE statement in Oracle allows you to perform an "upsert" operation, which inserts new rows from one table into another table or updates existing rows if they already exist. For example:

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MERGE INTO target_table
USING source_table
ON (target_table.common_column = source_table.common_column)
WHEN MATCHED THEN UPDATE SET target_table.column1 = source_table.column1
WHEN NOT MATCHED THEN INSERT (column1, column2) VALUES (source_table.column1, source_table.column2);

These are some of the ways you can merge data from two tables in Oracle. The best method to use will depend on the specific requirements of your task.