INSERT + SELECT data type mismatch on similar fields - sql

Question

I'm running the following SQLite workaround to add a primary key to a table that did not have one. I am getting a datatype mismatch on
INSERT INTO cities
SELECT id, name FROM old_cities;
However, the fields have exactly the same type. Is it possible that his happens due to running the queries from DbBrowser for SQLite?
CREATE table cities (
id INTEGER NOT NULL,
name TEXT NOT NULL
);
INSERT INTO cities (id, name)
VALUES ('pan', 'doul');
END TRANSACTION;
PRAGMA foreign_keys=off;
BEGIN TRANSACTION;
ALTER TABLE cities RENAME TO old_cities;
--CREATE TABLE cities (
-- id INTEGER NOT NULL PRIMARY KEY,
-- name TEXT NOT NULL
--);
CREATE TABLE cities (
id INTEGER NOT NULL,
name TEXT NOT NULL,
PRIMARY KEY (id)
);
SELECT * FROM old_cities;
INSERT INTO cities
SELECT id, name FROM old_cities;
DROP TABLE old_cities;
COMMIT;

Answer 1

You have defined the column id of the table cities to be INTEGER, but with this:
INSERT INTO cities (id, name) VALUES ('pan', 'doul');
you insert the string 'pan' as id.
SQLite does not do any type checking in this case and allows it.
Did you mean to insert 2 rows each having the names 'pan' and 'doul'?
If so, you should do something like:
INSERT INTO cities (id, name) VALUES (1, 'pan'), (2, 'doul');
Later you rename the table cities to old_cities and you recreate cities but you do something different: you define id as INTEGER and PRIMARY KEY.
This definition is the only one that forces type checking in SQLite.
So, when you try to insert the rows from old_cities to cities you get an error because 'pan' is not allowed in the column id as it is defined now.