SQL Anomaly Using 'USING' Clause with Nested Queries? - sql

Question

I have a normalized database containing 3 tables whose DDL is this:
CREATE CACHED TABLE Clients (
cli_id INTEGER GENERATED ALWAYS AS IDENTITY (START WITH 100) PRIMARY KEY,
defmrn_id BIGINT,
lastName VARCHAR(48) DEFAULT '' NOT NULL,
midName VARCHAR(24) DEFAULT '' NOT NULL,
firstName VARCHAR(24) DEFAULT '' NOT NULL,
doB INTEGER DEFAULT 0 NOT NULL,
gender VARCHAR(1) NOT NULL);
CREATE TABLE Client_MRNs (
mrn_id BIGINT GENERATED ALWAYS AS IDENTITY (START WITH 100) PRIMARY KEY,
cli_id INTEGER REFERENCES Clients ( cli_id ),
inst_id INTEGER REFERENCES Institutions ( inst_id ),
mrn VARCHAR(32) DEFAULT '' NOT NULL,
CONSTRAINT climrn01 UNIQUE (mrn, inst_id));
CREATE TABLE Institutions (
inst_id INTEGER GENERATED ALWAYS AS IDENTITY (START WITH 100) PRIMARY KEY,
loc_id INTEGER REFERENCES Locales (loc_id ),
itag VARCHAR(6) UNIQUE NOT NULL,
iname VARCHAR(80) DEFAULT '' NOT NULL);
The first table contains a foreign key column, defmrn_id, that is a reference to a "default identifier code" that is stored in the second table (which is a list of all identifier codes). A record in the first table may have many identifiers, but only one default identifier. So yeah, I have created a circular reference.
The third table is just normalized data from the second table.
I wanted a query that would find a CLIENT record based on matching a supplied identifier code to any of the identifier codes in CLIENT_MRNs that may belong to that CLIENT record.
My strategy was to first identify those records that matched in the second table (CLIENT_MRN) and then use that intermediate result to join to records in the CLIENT table that matched other user-supplied searching criteria. I also need to denormalize the identifier reference defmrn_id in the 1st table. Here is what I came up with...
SQL = SELECT c.*, r.mrn, i.inst_id, i.itag, i.iname
FROM Clients AS c
INNER JOIN
(
SELECT m.cli_id
FROM Client_MRNs AS m
WHERE m.mrn = ?
) AS m2 ON m2.cli_id = c.cli_id
INNER JOIN Client_MRNs AS r ON c.defmrn_id = r.mrn_id
INNER JOIN Institutions AS i USING ( inst_id )
WHERE (<other user supplied search criteria...>);
The above works, but I spent some time trying to understand why the following was NOT working...
SQL = SELECT c.*, r.mrn, i.inst_id, i.itag, i.iname
FROM Clients AS c
INNER JOIN
(
SELECT m.cli_id
FROM Client_MRNs AS m
WHERE m.mrn = ?
) AS m2 USING ( cli_id )
INNER JOIN Client_MRNs AS r ON c.defmrn_id = r.mrn_id
INNER JOIN Institutions AS i USING ( inst_id )
WHERE (<other user supplied search criteria...>);
It seems to me that the second SQL should work, but it fails on the USING clause every time. I am executing these queries against a database managed by HSQLDB 2.2.9 as the RDBMS. Is this a parsing issue in HSQLDB or is this a known limitation of the USING clause with nested queries?

Answer 1

You can always try with HSQLDB 2.3.0 (a release candidate).
The way you report the incomplet SQL does not allow proper checking. But there is an ovbious mistake in the query. If you have:
SELECT INST_ID FROM CLIENTS_MRS AS R INNER JOIN INSTITUTIONS AS I USING (INST_ID)
INST_ID can be used in the SELECT column list only without a table qualifier. The reason is it is no longer considered a column of either table. The same is true with common columns if you use NATURAL JOIN.
This query is accepted by version 2.3.0
SELECT c.*, r.mrn, inst_id, i.itag, i.iname
FROM Clients AS c
INNER JOIN
(
SELECT m.cli_id
FROM Client_MRNs AS m
WHERE m.mrn = 2
) AS m2 USING ( cli_id )
INNER JOIN Client_MRNs AS r ON c.defmrn_id = r.mrn_id
INNER JOIN Institutions AS i USING ( inst_id )