[SalesForce] Update boolean value in data extension from false to true with Sql Query

EDIT

Based on the comments below, this may be your best answer:

SELECT *
FROM SourceDE s
LEFT JOIN DestinationDE d
ON s.PrimaryKey = d.PrimaryKey
WHERE d.PrimaryKey IS NULL

This will force an Update type, but as there will be no duplicates due to the above LeftJoin and Where statement, this will only add to the Destination DE and not update records.

SQL queries in SFMC use the APPEND option to do an add only function.

Append - Adds the query results to the data extension after existing records.

Update - Updates records in the data extension with query results and appends non-matching records.

Overwrite - Delete the data extension's records and add the query results.

(ref from the SFMC help docs)

So, basically you just need to set your type to APPEND and you should be fine with adding to your DE.

You say in Extended all boolean values are empty, so they are NULL. I believe making a Field != 'value' statement in SQL includes all other records where Field has a value different from 'value', but it does not include records where Field has no value.

Your second query returns results because of e.Boolean IS NULL.

I hope that helps.

By the way: Are you sure OptIn in Basic is defined as a Boolean and not as a string? I am surprised b.OptIn = 'True' would give any results if Basic is defined as a boolean. We created a product that helps users build selections through a UI without having to write SQL queries. In the queries our product builds, we always use 0 for False and 1 for True when comparing Boolean values.