Replace foreign key IDs in table with values from those tables - mysql

Question

I have a database I extracted from an application (I did not create it). I need to extract the data to use in a different application. The main table contains 3 foreign keys each linking to other tables. I want to replace the FK IDs with a specific column value from those other tables. The main table looks like this:
data:
+------------+------------+--------+----------+-----------+----------+------+
| startdate | enddate | status | employee | cause | duration | type |
+------------+------------+--------+----------+-----------+----------+------+
| 2018-01-05 | 2018-01-07 | 2 | 1 | some text | 3 | 1 |
+------------+------------+--------+----------+-----------+----------+------+
| 2018-02-03 | 2018-02-04 | 1 | 2 | some text | 2 | 2 |
+------------+------------+--------+----------+-----------+----------+------+
status, employee and type are all foreign keys. They link to tables with the following layouts:
users:
+----+-----------+----------+
| id | firstname | lastname |
+----+-----------+----------+
| 1 | John | Doe |
+----+-----------+----------+
| 2 | Dylan | Smith |
+----+-----------+----------+
types:
+----+-----------+
| id | name |
+----+-----------+
| 1 | Annual |
+----+-----------+
| 2 | Quarterly |
+----+-----------+
status:
+----+----------+
| id | name |
+----+----------+
| 1 | Accepted |
+----+----------+
| 2 | Rejected |
+----+----------+
I want the main table to then look like this is
+------------+------------+-----------+--------------+-----------+----------+-----------+
| startdate | enddate | status | employee | cause | duration | type |
+------------+------------+-----------+--------------+-----------+----------+-----------+
| 2018-01-05 | 2018-01-07 | Rejected | John Doe | some text | 3 | Annual |
+------------+------------+-----------+--------------+-----------+----------+-----------+
| 2018-02-03 | 2018-02-04 | Accepted | Dylan Smith | some text | 2 | Quarterly |
+------------+------------+-----------+--------------+-----------+----------+-----------+
I've tried various things I've found on Google as well as SO but I can't get it to come out the way I want it to. I come from a PHP background but I have some experience in SQL, but I am not an expert. I've tried getting the values corresponding to the IDs and saving them in a different table, but I don't know how I can update the table with those returned values:
INSERT into stat
SELECT b.name stat
FROM data a JOIN status b
ON a.status = b.id
This creates a column with the right values in the right order in a table called "stat", like so:
+----------+
| status |
+----------+
| Rejected |
+----------+
| Accepted |
+----------+
This works similarly for the "users" (I also concatenate the first name and last names into a column called "name" in a "user" table. I want to use the concatenated value) and "types" tables. How can I update each respective FK value in the "data" table with their respective values as in the tables above?

Answer 1

Joining from the data table to the three other tables should work here:
SELECT
d.startdate,
d.enddate,
s.name AS status,
CONCAT(u.firstname, ' ', u.lastname) AS employee,
d.cause,
d.duration,
t.name AS type
FROM data d
LEFT JOIN status s
ON d.status = s.id
LEFT JOIN users u
ON d.employee = u.id
LEFT JOIN types t
ON d.type = t.id;
If a given value coming in from one of the joins be missing, and you want to display a placeholder value (instead of the default NULL), then you may use the COALESCE function.