Tag Archives: SQL

Select Latest Data from Table

Problem Given the following database table: DATA (id, data_date, data_value). The id field is not unique. Write an SQL statement to select the latest value for each id Solution Group rows by id then select rows with maximum date Code …

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How to Find Duplicates in a Table using SQL

Problem Write an SQL statement to find rows with duplicate column values in a database table Solution You need to group by the column containing the duplicate values then select only the groups with count greater than 1 Code Here …

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Delete Table vs Truncate Table

Question What is the difference between delete table and truncate table operation Answer Delete table operation deletes all rows in the table. The deletion of rows is logged in the transaction log. On the other hand truncate table operation similarly …

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Sql Query Optimization

Question Suggest few areas to inspect to improve the performance of a slow query Answer Here are few areas to check: Tables have no indexes. Database indexes improve query performance dramatically on the expense of slow writes and extra space …

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Where vs Having SQL

Question What is the difference between WHERE and HAVING clauses. Answer The WHERE clause restricts which rows are returned while the HAVING clause operates on groups of rows. HAVING is always used with GROUP BY and must have a function …

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Sql Views Advantages

Question What is a database view. Mention few database sql views advantages Answer A view is a virtual table (not part of the physical schema) composed from the result set of a stored query. Views contain dynamic content. This means if you modify the physical …

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SQL All Keyword

All Keyword in SQL Given the following database table: employee(emp_name, emp_salary) write an SQL statement to print the employee name with the highest salary Solution Using the max aggregate function will give us the maximum salary but it does not …

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