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Oracle 12c: SQL
In Oracle, you can group query results based on a particular column using the GROUP BY clause in a SQL query. To group query results based on a job column, you can use a query like:
SELECT job, COUNT(*) as total FROM employees GROUP BY job;
This query will group all the employees based on their job titles and count the total number of employees in each job category. You can replace the 'employees' table and 'job' column with the actual table and column names in your database schema. This will provide you with a result set showing the job titles and the total number of employees in each job category.
How to join tables in a grouped query in Oracle?
To join tables in a grouped query in Oracle, you can use the JOIN clause along with the GROUP BY clause. Here's an example of how you can join two tables and group the data:
SELECT table1.column1, table2.column2, SUM(table1.column3) FROM table1 JOIN table2 ON table1.column1 = table2.column1 GROUP BY table1.column1, table2.column2;
In this example, table1 and table2 are the tables you want to join. You use the JOIN keyword to specify the join condition, which in this case is table1.column1 = table2.column1. The SELECT statement selects the columns you want to include in the result set and performs an aggregate function (SUM) on one of the columns. Finally, the GROUP BY clause groups the results based on the specified columns.
How to group query based on job in Oracle?
To group queries based on job in Oracle, you can use the GROUP BY clause in your SQL query. Here's an example:
SELECT job, COUNT(*) as num_employees FROM employees GROUP BY job;
In this query, we are selecting the job title from the employees table and counting the number of employees with each job title. The GROUP BY clause groups the results by the job title, so you will get a count of employees for each unique job title in the table.
What is the advantage of using the ROLLUP function in a query in Oracle?
The ROLLUP function in Oracle allows you to generate subtotals for rows and columns in the result set. This can be useful when you want to display summarized data in addition to detailed data in a single query.
Using the ROLLUP function can help you easily create a report that shows both detailed and summary information without having to write multiple queries or perform additional aggregation in your application code. It simplifies the process of generating reports and analyzing data, making it a powerful tool for data analysis and reporting in Oracle.
Overall, the advantage of using the ROLLUP function in a query is that it provides a convenient way to generate subtotal and grand total values in the result set, allowing you to gain insights from your data more efficiently.