In SQLite, the CREATE TEMPORARY TABLE statement is used to create a temporary table. Temporary tables are similar to regular tables but are only visible and accessible to the session that creates them. They are automatically dropped when the session ends or when explicitly dropped by the user. This makes temporary tables a convenient tool for storing intermediate results during complex queries or for temporary storage needs.
Here is the basic syntax for creating a temporary table in SQLite:
CREATE TEMPORARY TABLE [IF NOT EXISTS] temp_table_name ( column1 datatype1, column2 datatype2, ... );
Let’s break down the components of this syntax:
CREATE TEMPORARY TABLE: This part of the statement indicates that you want to create a temporary table.
[IF NOT EXISTS]: This is an optional clause that allows you to check if the temporary table already exists before creating it. If the table already exists and the IF NOT EXISTS clause is used, SQLite will not return an error. If the clause is omitted, an error will be raised if the table already exists.
temp_table_name: This is the name you give to your temporary table. It follows the same naming rules as regular tables.
(column1 datatype1, column2 datatype2, …): This section defines the columns of the temporary table along with their data types. You specify the names and data types of the columns when creating the table.
Here’s a simple example:
CREATE TEMPORARY TABLE IF NOT EXISTS temp_employee ( employee_id INTEGER, employee_name TEXT, salary REAL );
In this example, a temporary table named temp_employee is created with columns for employee_id (integer), employee_name (text), and salary (real).
Once you have created a temporary table, you can perform various operations on it, such as inserting data, updating records, or querying information. Remember that the temporary table is only accessible within the session that created it, and it will be automatically dropped when the session ends or when explicitly dropped using the DROP TABLE statement.
-- Example of inserting data into the temporary table INSERT INTO temp_employee VALUES (1, 'John Doe', 50000.00); -- Example of querying data from the temporary table SELECT * FROM temp_employee;
After the session is completed, the temporary table temp_employee and its data will be automatically dropped, freeing up resources and preventing interference with other sessions or transactions.