SQL query to select group then order from 2 tables - sql

Question

Here are the tables
TAGS :
tag_id
tag_name
1
SENT
2
AIRTIME
3
RECEIVED
4
KOPOKOPO
5
RESTAURANT
6
PAID
7
UBER
TRANS_TAG
tag_id
trans_id
1
1
2
1
3
1
4
1
5
1
6
1
1
2
2
2
3
2
4
2
5
2
6
2
The following are default tags (SENT, AIRTIME, RECEIVED, PAID), the rest are not default tags.
The TRANS_TAG table tracks a transaction id and the tags attached to it.
I would like to write a select SQL statement that selects from these two tables and achieves the following result. - it returns a list of all the tags that have been attached to at least one transaction. it then orders them alphabetically but grouped with the default tags first.
This is the desired result
tag_name
AIRTIME
PAID
RECIVED
SENT
KOPOKOPO
RESTAURANT
This is the code that I have so far
String SQL = "SELECT "
+ KEY_TAG_TITLE +
" FROM " + TABLE_TRANS_TAG
+ " INNER JOIN " + TABLE_TAG + " " + "ON " + TABLE_TRANS_TAG + "." + KEY_TRANS_TAG_TAG_ID
+ " = " + TABLE_TAG + "." + KEY_TAG_ID
+ " GROUP BY " + KEY_TAG_TITLE
+ " ORDER BY " + TABLE_TAG + "." + KEY_TAG_TITLE + " ASC, " + TABLE_TAG + "." + KEY_ROW_ID + " ASC";

Answer 1

You can use:
SELECT T.KEY_TAG_TITLE
FROM TABLE_TRANS_TAG TT INNER JOIN
TABLE_TAG T
ON TT.KEY_TRANS_TAG_TAG_ID = T.KEY_TAG_ID
GROUP BY T.KEY_TAG_TITLE
ORDER BY (CASE WHEN T.KEY_TAG_TITLE IN ('SENT', 'AIRTIME', 'RECEIVED', 'PAID') THEN 1 ELSE 2 END),
T.KEY_TAG_TITLE;

Answer 2

Don't use join and aggregation for such a simple requirement.
It would result in poor performance.
Use EXISTS and conditional sorting:
String SQL = "SELECT tg." + KEY_TAG_TITLE + " " +
"FROM " + TABLE_TAG + " AS tg " +
"WHERE EXISTS (SELECT 1 FROM " + TABLE_TRANS_TAG + " AS tr WHERE tr." + KEY_TRANS_TAG_TAG_ID + " = tg." + KEY_TAG_ID + ") " +
"ORDER BY tg." + KEY_TAG_TITLE + " IN ('SENT', 'AIRTIME', 'RECEIVED', 'PAID') DESC, tg." + KEY_TAG_TITLE;