How to Join 2 Tables In Oracle Sql?

To join two tables in Oracle SQL, you use the JOIN keyword in your query. The most common type of join is the INNER JOIN, which returns rows when there is at least one match in both tables.

To perform an INNER JOIN, you specify the tables you want to join and the columns you want to join on using the ON keyword. For example:

SELECT * FROM table1 JOIN table2 ON table1.column_name = table2.column_name;

You can also use other types of joins such as LEFT JOIN, RIGHT JOIN, and FULL JOIN based on your specific requirements. Joins allow you to combine data from multiple tables to retrieve the desired results in a single query.

What is the difference between INNER JOIN and OUTER JOIN in Oracle SQL?

INNER JOIN and OUTER JOIN are two types of join operations used in Oracle SQL to combine rows from two or more tables based on a related column between them. The main difference between INNER JOIN and OUTER JOIN is in how they handle unmatched rows between the tables being joined.

1. INNER JOIN:

• INNER JOIN returns only the rows that have matching values in both tables based on the specified join condition.
• If there is no match found for a row in one of the tables, that row is not included in the result set.
• INNER JOIN is the default type of join in SQL and is used when you only want to retrieve rows that have corresponding values in both tables.

Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column_name = table2.column_name;

1. OUTER JOIN:

• OUTER JOIN returns all the rows from one table (the "outer" table) and only the matching rows from the other table (the "inner" table) based on the join condition.
• If there is no match found for a row in one of the tables, NULL values are returned for columns from the other table.
• There are three types of OUTER JOIN: LEFT OUTER JOIN (or LEFT JOIN), RIGHT OUTER JOIN (or RIGHT JOIN), and FULL OUTER JOIN.

Example of LEFT OUTER JOIN: SELECT * FROM table1 LEFT OUTER JOIN table2 ON table1.column_name = table2.column_name;

In summary, INNER JOIN only returns rows with matching values in both tables, while OUTER JOIN returns all rows from one table and only matching rows from the other table, including NULL values for unmatched rows.

What is the difference between NATURAL JOIN and JOIN ON in Oracle SQL?

In Oracle SQL, the NATURAL JOIN and JOIN ON are both used to combine data from two or more tables. However, there are differences between the two:

1. NATURAL JOIN:

• Automatically joins the tables based on columns with the same name and datatype.
• Only columns that are present in both tables and have the same name and datatype are used in the join.
• There is no need to specify the columns to join on, as the join is done based on the common columns automatically.
• May result in unexpected or undesired results if there are multiple columns with the same name in the tables being joined.

1. JOIN ON:

• Requires explicitly specifying the columns to join on using the ON keyword.
• Allows more control over the join conditions and the columns used for joining.
• Can be used to join tables on columns that do not have the same name or datatype.
• Provides a more explicit and flexible way to define the join conditions.

In general, JOIN ON is preferred over NATURAL JOIN when more control and clarity is needed in specifying the join conditions.

How to join 2 tables in Oracle SQL with multiple conditions?

To join two tables in Oracle SQL with multiple conditions, you can use the JOIN keyword along with the ON keyword to specify the conditions for the join. Here is an example of how to join two tables with multiple conditions:

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SELECT t1.column1, t2.column2
FROM table1 t1
JOIN table2 t2
ON t1.column3 = t2.column4
AND t1.column5 = t2.column6;

In this example, table1 and table2 are the names of the two tables you want to join. t1 and t2 are aliases for the tables to make the query more readable. The ON keyword is used to specify the conditions for the join, in this case, joining the tables where column3 from table1 is equal to column4 from table2 and column5 from table1 is equal to column6 from table2.

You can add more conditions to the ON clause by using additional AND or OR operators as needed to further refine the join criteria.

How to join 2 tables in Oracle SQL using CROSS JOIN?

You can join two tables in Oracle SQL using CROSS JOIN by following these steps:

1. Write a SELECT statement and specify the columns you want to retrieve from both tables.
2. Use the CROSS JOIN keyword to combine the rows of both tables without any conditional statements.
3. Specify the tables you want to join and give them aliases to differentiate between them in the SELECT statement.
4. Here is an example of how to join two tables using CROSS JOIN in Oracle SQL:

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SELECT t1.column1, t1.column2, t2.column1, t2.column2
FROM table1 t1
CROSS JOIN table2 t2;

In this example, "table1" and "table2" are the names of the tables you want to join. "t1" and "t2" are the aliases given to these tables to refer to them in the SELECT statement. The SELECT statement retrieves columns from both tables using the aliases.

Note that a CROSS JOIN combines every row from the first table with every row from the second table, resulting in a Cartesian product of the two tables. Make sure to use this type of join when you specifically want to combine all rows from both tables.

How to join 2 tables in Oracle SQL using FULL JOIN?

To join 2 tables in Oracle SQL using a FULL JOIN, you can follow the steps below:

1. Write a SELECT statement that includes the columns you want to retrieve from both tables.
2. Specify the tables you want to join in the FROM clause, and use the FULL JOIN keyword to indicate that you want to perform a full join.
3. Specify the join condition in the ON clause, which indicates how the two tables should be matched.
4. Optional: Use the WHERE clause to further filter the result set if needed.

Here is an example of joining two tables using a FULL JOIN in Oracle SQL:

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

In this example, replace table1, table2, column1, column2, column3, and common_column with the actual table and column names you are working with. This query will return a result set that includes all rows from both tables, with matching records joined together and any unmatched records from either table also included in the result.