SQLite - UPSERT *not* INSERT or REPLACE

Question

http://en.wikipedia.org/wiki/Upsert

Insert Update stored proc on SQL Server

Is there some clever way to do this in SQLite that I have not thought of?

Answer 1

This method remixes a few of the other methods from answer in for this question and incorporates the use of CTE (Common Table Expressions). I will introduce the query then explain why I did what I did.

I would like to change the last name for employee 300 to DAVIS if there is an employee 300. Otherwise, I will add a new employee.

Table Name: employees Columns: id, first_name, last_name

The query is:

INSERT OR REPLACE INTO employees (employee_id, first_name, last_name)
WITH registered_employees AS ( --CTE for checking if the row exists or not
    SELECT --this is needed to ensure that the null row comes second
        *
    FROM (
        SELECT --an existing row
            *
        FROM
            employees
        WHERE
            employee_id = '300'

        UNION

        SELECT --a dummy row if the original cannot be found
            NULL AS employee_id,
            NULL AS first_name,
            NULL AS last_name
    )
    ORDER BY
        employee_id IS NULL --we want nulls to be last
    LIMIT 1 --we only want one row from this statement
)
SELECT --this is where you provide defaults for what you would like to insert
    registered_employees.employee_id, --if this is null the SQLite default will be used
    COALESCE(registered_employees.first_name, 'SALLY'),
    'DAVIS'
FROM
    registered_employees
;

Basically, I used the CTE to reduce the number of times the select statement has to be used to determine default values. Since this is a CTE, we just select the columns we want from the table and the INSERT statement uses this.

Now you can decide what defaults you want to use by replacing the nulls, in the COALESCE function with what the values should be.