SQLite CRUD Operation: Select Query

The SELECT statement in SQLite is used to fetch the data from one or more tables. It allows you to retrieve specific data based on a set of conditions and can also be used to sort, group, and aggregate data.

Syntax

The syntax of the SELECT statement in SQLite is as follows:

SELECT column1, column2, .... columnN FROM table_name WHERE [condition];

Here, column1, column2, .... columnN are the names of the columns that you want to retrieve from the table, and table_name is the name of the table that you want to query. The WHERE clause is optional and is used to specify the conditions that the data must meet in order to be retrieved.

Example

Suppose we have a table called students with the following columns: id, name, age, and grade, and we want to retrieve the names and ages of all the students who have a grade of A. We can use the following SELECT statement:

SELECT name, age FROM students WHERE grade='A';

Output

The output of the SELECT statement will be a list of all the students who have a grade of A, along with their names and ages:

| Name   | Age |
|--------|-----|
| Alice  | 19  |
| Bob    | 18  |
| Carol  | 21  |

Explanation

In the example above, we use the SELECT statement to retrieve the names and ages of all students who have a grade of A. We specify the columns that we want to retrieve in the SELECT clause (name and age) and the table that we want to query (students). We also use the WHERE clause to specify the condition that the grade column must be equal to A. The result is a list of students who meet the specified condition.

Use

The SELECT statement in SQLite is used to retrieve specific data from one or more tables. It's commonly used in applications to display data to users or to retrieve data for further processing. The SELECT statement can be combined with other SQL clauses, such as ORDER BY, GROUP BY, and HAVING, to sort and aggregate data as needed.

Important Points

• The SELECT statement can also be used to retrieve all columns from a table by using the * wildcard character in the SELECT clause.
• You can use the ORDER BY clause to sort the results of a SELECT statement by one or more columns.
• The GROUP BY clause is used to group the data by one or more columns.
• The HAVING clause is used to filter the results of a GROUP BY query based on a condition.
• The DISTINCT keyword is used to eliminate duplicate rows from the results.

Summary

In this tutorial, we learned about the SELECT statement in SQLite and how to use it to retrieve specific data from one or more tables. We saw an example of how to retrieve the names and ages of all students who have a grade of A from a table called students. We also learned about some advanced SQL clauses, such as ORDER BY, GROUP BY, HAVING, and DISTINCT, that can be used in combination with the SELECT statement to sort, group, and filter data.