SQLITE date no type checked

Question

I just tested sqlite and created a table.

$sqlite3 plop.db

sqlite> CREATE TABLE t (d DATE);

sqlite> INSERT INTO t (d) VALUES (\'Hello\');

sqlite>         


        

Answer 1

SQLite DATE type has NUMERIC affinity. Despite its name, the NUMERIC affinity allows storing data of all five storage classes (NULL, INTEGER, REAL, TEXT, and BLOB). A column that has NUMERIC affinity (e.g. a DATE column) tries to convert any text data to INTEGER and REAL first. If this conversion is possible, it stores data using INTEGER or REAL storage classes respectively. If conversion is not possible, the data is stored using TEXT storage class. And this is exactly what happened in your case. See http://www.sqlite.org/datatype3.html#affinity

Answer 2

From Sqlite's Frequently Asked Questions

SQLite lets me insert a string into a database column of type integer!

This is a feature, not a bug. SQLite uses dynamic typing. It does not enforce data type constraints. Any data can be inserted into any column. You can put arbitrary length strings into integer columns, floating point numbers in boolean columns, or dates in character columns. The datatype you assign to a column in the CREATE TABLE command does not restrict what data can be put into that column. Every column is able to hold an arbitrary length string. (There is one exception: Columns of type INTEGER PRIMARY KEY may only hold a 64-bit signed integer. An error will result if you try to put anything other than an integer into an INTEGER PRIMARY KEY column.)

But SQLite does use the declared type of a column as a hint that you prefer values in that format. So, for example, if a column is of type INTEGER and you try to insert a string into that column, SQLite will attempt to convert the string into an integer. If it can, it inserts the integer instead. If not, it inserts the string. This feature is called type affinity.