1. Q: What is SQL?
A: SQL (Structured Query Language) is a programming language used to manage and manipulate relational databases.
2. Q: What are the different types of SQL statements?
A: The different types of SQL statements are:
- SELECT: Retrieves data from a database.
- INSERT: Inserts new data into a database.
- UPDATE: Modifies existing data in a database.
- DELETE: Deletes data from a database.
- CREATE: Creates a new database, table, or other database objects.
- ALTER: Modifies the structure of a database object.
- DROP: Deletes a database object.
3. Q: What is the syntax for the SELECT statement?
A: The syntax for the SELECT statement is as
follows: SELECT column1, column2 FROM table_name WHERE condition;
4. Q: How do you retrieve all records from a table?
A: To retrieve all records from a table, you can use the following SELECT
statement: SELECT * FROM table_name;
5. Q: How do you filter records based on a specific condition in the WHERE clause?
A: To filter records based on a specific condition, you can use the following SELECT
statement: SELECT column1, column2 FROM table_name WHERE condition;
6. Q: How do you sort records in ascending or descending order?
A: To sort records in ascending order, you can use the ORDER BY keyword followed by the column name. For descending order, use ORDER BY column_name DESC.
Example: SELECT column1, column2 FROM table_name ORDER BY column1 ASC;
7. Q: How do you insert new records into a table?
A: To insert new records into a table, you can use the INSERT INTO statement.
Example: INSERT INTO table_name (column1, column2) VALUES (value1, value2);
8. Q: How do you update existing records in a table?
A: To update existing records in a table, you can use the UPDATE statement.
Example: UPDATE table_name SET column1 = value1, column2 = value2 WHERE condition;
9. Q: How do you delete records from a table?
A: To delete records from a table, you can use the DELETE statement.
Example: DELETE FROM table_name WHERE condition;
10. Q: How do you join two or more tables together?
A: To join tables, you can use the JOIN keyword followed by the table names and the join condition.
Example: SELECT column1, column2 FROM table1 JOIN table2 ON table1.column = table2.column;
11. Q: What is the difference between INNER JOIN and OUTER JOIN?
A: An INNER JOIN returns only the matching records from both tables, while an OUTER JOIN returns all records from one table and the matching records from the other table.
12. Q: How do you count the number of records in a table?
A: To count the number of records in a table, you can use the COUNT() function.
Example: SELECT COUNT(*) FROM table_name;
13. Q: How do you group records based on a specific column?
A: To group records based on a specific column, you can use the GROUP BY clause.
Example: SELECT column1, COUNT(column2) FROM table_name GROUP BY column1;
14. Q: How do you find the maximum or minimum value in a column?
A: To find the maximum value, you can use the MAX() function. To find the minimum value, use the MIN() function.
Example: SELECT MAX(column1) FROM table_name;
SELECT MIN(column2) FROM table_name;
15. Q: How do you calculate the average or sum of a column?
A: To calculate the average, use the AVG() function. To calculate the sum, use the SUM() function.
Example: SELECT AVG(column1) FROM table_name;
SELECT SUM(column2) FROM table_name;
16. Q: How do you add a new column to an existing table?
A: To add a new column to an existing table, you can use the ALTER TABLE statement.
Example: ALTER TABLE table_name ADD column_name datatype;
17. Q: How do you modify the data type of a column in a table?
A: To modify the data type of a column in a table, you can use the ALTER TABLE statement with the MODIFY clause.
Example: ALTER TABLE table_name MODIFY column_name new_datatype;
18. Q: How do you delete a table from a database?
A: To delete a table from a database, you can use the DROP TABLE statement.
Example: DROP TABLE table_name;
19. Q: How do you create a new database?
A: To create a new database, you can use the CREATE DATABASE statement.
Example: CREATE DATABASE database_name;
20. Q: How do you select distinct values from a column?
A: To select distinct values from a column, you can use the DISTINCT keyword.
Example: SELECT DISTINCT column_name FROM table_name;