Coalesce pulling zero as value - mysql

Question

this is driving me crazy!
I have three tables. The first table has a list of all records along with other data (region, dates, etc). The 2nd and 3rd tables have all the hours/cost data, but the 2nd table contains only historical records, and the 3rd table contains newer records. I want my coalesce to try to find a value in the newer records first, but if no record is found, to look in the historic table. For some reason, even though i KNOW there is a value in the historic table, the result of my coalesce is coming in as 0.
Table1
ID Region
1 US
2 US
3 Europe
4 US
5 Europe
6 US
Table2
ID Hours
1 10
2 15
3 20
Table3
ID Hours
4 3
5 7
6 4
So, my statement is written like this:
SELECT
t1.ID,
COALESCE(t3.hours, t2.hours) AS HOURS
FROM table1 t1
LEFT JOIN table2 t2
ON t1.ID=t2.ID
LEFT JOIN table3 t3
ON t1.ID=t3.ID
Now, for some reason, if the value is found in t3 (the newer records) it pulls in the correct value, but if it does not find a value and has to pull in a value from t2, it is pulling in a 0 instead of the actual value. Result looks like this:
ID HOURS
1 0
2 0
3 0
4 3
5 7
6 4
My guess is that it has something to do with the column type in table 2 (I have all column settings as VARCHAR(55), but I can't find any rules around data types in coalesce function about having to use only a certain column type with coalesce.
Appreciate any guidance!
edited to add results for Spencer's inquiry:
ID t2.hours + 0 t2.hours hex(t2.hours) length(t2.hours)
413190 240 240 F0 3

Answer 1

Incorrect joins:
FROM table1 t1
LEFT JOIN table2 t2 ON t1.ID=t2.ID
^
LEFT JOIN table3 t3 ON t1.ID=t2.ID
^
you're joining table 3 using values from table 2

Answer 2

It looks like the evaluation of t2.hours in the COALESCE function is being done in numeric context, and the values stored in the hours column are evaluating to a numeric value of 0.
One quick way to check what numeric that evaluates to is to add a zero, as in the first expression in this query:
SELECT t2.hours + 0
, t2.hours
, HEX(t2.hours)
, LENGTH(t2.hours)
FROM table2 t2
I'm curious what that query shows for one of the rows that's returning a 0 from the COALESCE expression, whether the numeric evaluation is returning 0, and whether there's any leading wonky characters in the column value.