It would be helpful if the following two tables had a specific constraint:
-- Table: privilege_group
CREATE TABLE privilege_group (
privilege_group_id integer NOT NULL CONSTRAINT privilege_group_pk PRIMARY KEY AUTOINCREMENT,
name text NOT NULL,
CONSTRAINT privilege_group_name UNIQUE (name)
);
-- Table: privilege_relationship
CREATE TABLE privilege_relationship (
privilege_relationship_id integer NOT NULL CONSTRAINT privilege_relationship_pk PRIMARY KEY AUTOINCREMENT,
parent_id integer NOT NULL,
child_id integer NOT NULL,
CONSTRAINT privilege_relationship_parent_child UNIQUE (parent_id, child_id),
CONSTRAINT privilege_relationship_parent_id FOREIGN KEY (parent_id)
REFERENCES privilege_group (privilege_group_id),
CONSTRAINT privilege_relationship_child_id FOREIGN KEY (child_id)
REFERENCES privilege_group (privilege_group_id),
CONSTRAINT privilege_relationship_check CHECK (parent_id != child_id)
);
Each parent can have multiple children, and each child can have multiple parents. Processing relationships can be done outside of the database, but is there a way within the database to prevent recursive relationships?
My research shows that it is possible to use CREATE TRIGGER and to use a RAISE function to prevent something from completing, but the possibility of internal depth-first or breadth-first searches in SQLite3 is unknown to me.
Related
I'm running into org.sqlite.SQLiteException: [SQLITE_ERROR] SQL error or missing database (foreign key mismatch - ... with a statement, that proceeds without any complaints using the normal SQLite-frontend. This creates the crucial part of my database:
CREATE TABLE IF NOT EXISTS artists (
aid INTEGER PRIMARY KEY AUTOINCREMENT,
aname VARCHAR(200) NOT NULL,
CONSTRAINT one UNIQUE(aname)
);
CREATE TABLE IF NOT EXISTS discs (
did INTEGER PRIMARY KEY AUTOINCREMENT,
testAddCD1 BIGINT(10) NOT NULL,
dtitle VARCHAR(125) NOT NULL,
dreleaseyear YEAR(4) DEFAULT NULL,
dlang VARCHAR(3) DEFAULT NULL
);
CREATE TABLE IF NOT EXISTS tracks (
discs_did INTEGER NOT NULL,
tnumber INT(4) NOT NULL,
ttitle VARCHAR(125) NOT NULL,
tseconds INT(4) NOT NULL,
CONSTRAINT pk PRIMARY KEY(discs_did, tnumber),
CONSTRAINT fk FOREIGN KEY(discs_did) REFERENCES discs(did) ON DELETE RESTRICT ON UPDATE RESTRICT,
CONSTRAINT val CHECK(tseconds> 0)
);
CREATE TABLE IF NOT EXISTS track_by_artist (
discs_did INTEGER NOT NULL,
tracks_tnumber INT(4) NOT NULL,
artists_aid INTEGER NOT NULL,
CONSTRAINT pk PRIMARY KEY(discs_did, tracks_tnumber, artists_aid),
CONSTRAINT fk1 FOREIGN KEY(discs_did) REFERENCES discs(did) ON DELETE RESTRICT ON UPDATE RESTRICT,
CONSTRAINT fk2 FOREIGN KEY(tracks_tnumber) REFERENCES tracks(tnumber) ON DELETE RESTRICT ON UPDATE RESTRICT,
CONSTRAINT fk3 FOREIGN KEY(artists_aid) REFERENCES artists(aid) ON DELETE RESTRICT ON UPDATE RESTRICT
The database gets created and the JDBC-driver inserts an artist, a disc and the disc's tracks - all good. The final insert should assign an artist to a track and looks like
INSERT INTO track_by_artist (discs_did, tracks_tnumber, artists_aid) VALUES (1, 1, 1);
Using the JDBC this yields
SQLite-Error #1
org.sqlite.SQLiteException: [SQLITE_ERROR] SQL error or missing database (foreign key mismatch - "track_by_artist" referencing "tracks")
at org.sqlite.core.DB.newSQLException(DB.java:1012)
at org.sqlite.core.DB.newSQLException(DB.java:1024)
at org.sqlite.core.DB.throwex(DB.java:989)
at org.sqlite.core.NativeDB.prepare_utf8(Native Method)
at org.sqlite.core.NativeDB.prepare(NativeDB.java:134)
at org.sqlite.core.DB.prepare(DB.java:257)
at org.sqlite.core.CorePreparedStatement.<init>(CorePreparedStatement.java:45)
at org.sqlite.jdbc3.JDBC3PreparedStatement.<init>(JDBC3PreparedStatement.java:30)
at org.sqlite.jdbc4.JDBC4PreparedStatement.<init>(JDBC4PreparedStatement.java:25)
at org.sqlite.jdbc4.JDBC4Connection.prepareStatement(JDBC4Connection.java:35)
at org.sqlite.jdbc3.JDBC3Connection.prepareStatement(JDBC3Connection.java:241)
at org.sqlite.jdbc3.JDBC3Connection.prepareStatement(JDBC3Connection.java:205)
Issuing the same SQL-Insert with SQLite's text-frontend works like cream.
I'm a little lost and don't know what to do about my Java-code.
Some advise, pls?
Chris
The problem is that in track_by_artist you defined this foreign key constraint:
CONSTRAINT fk2 FOREIGN KEY(tracks_tnumber) REFERENCES tracks(tnumber) ON DELETE RESTRICT ON UPDATE RESTRICT
although tnumber in tracks is not UNIQUE (and it shouldn't be).
A foreign key's parent must be defined as UNIQUE.
In tracks the PRIMARY KEY is defined as the combination of discs_did and tnumber, which makes sense, so the combination of these 2 columns is unique.
What you can do is define in track_by_artist a composite foreign key for the columns discs_did and tracks_tnumber that reference discs_did and tnumber of tracks:
CREATE TABLE IF NOT EXISTS track_by_artist (
discs_did INTEGER NOT NULL,
tracks_tnumber INT(4) NOT NULL,
artists_aid INTEGER NOT NULL,
CONSTRAINT pk PRIMARY KEY(discs_did, tracks_tnumber, artists_aid),
CONSTRAINT fk1 FOREIGN KEY(discs_did, tracks_tnumber) REFERENCES tracks(discs_did, tnumber) ON DELETE RESTRICT ON UPDATE RESTRICT,
CONSTRAINT fk2 FOREIGN KEY(artists_aid) REFERENCES artists(aid) ON DELETE RESTRICT ON UPDATE RESTRICT
);
This way you don't need a separate foreign key definition for discs_did.
I've read this question and understood the referenced foreign keys to be unique, but somehow the insertion to table are still throwing foreign key mismatch errors:
CREATE TABLE medication (
med_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
med_name VARCHAR (20) NOT NULL,
dosage VARCHAR (10)
);
CREATE TABLE disease (
dis_id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
disease_name VARCHAR (20) NOT NULL
);
CREATE TABLE dis_med (
disease_id int NOT NULL,
medication_id int NOT NULL,
CONSTRAINT PK_dis_med PRIMARY KEY (disease_id, medication_id),
CONSTRAINT FK_dis FOREIGN KEY (disease_id) REFERENCES disease (dis_id),
CONSTRAINT FK_med FOREIGN KEY (medication_id) REFERENCES medication (med_id));
CREATE TABLE user_disease (
user_id REFERENCES user (user_id),
dis_id REFERENCES disease (dis_id),
med_id REFERENCES dis_med(medication_id),
CONSTRAINT PK_dis_user PRIMARY KEY (user_id, dis_id)
);
Through the list in the question I cited:
the parent table (medication, disease) exists.
the parent columns exist
the child table references all of the primary key columns in the parent table
Update1
I was able to insert data and bypass the error by altering the user_disease table by composite foreign key. I'd appreciate it if someone can point out what's the best design here. Many thanks in advance!
CREATE TABLE user_disease (
user_id REFERENCES user (user_id),
dis_id REFERENCES disease (dis_id),
med_id REFERENCES dis_med(medication_id),
CONSTRAINT FK_dis_med FOREIGN KEY REFERENCES dis_med(disease_id, medication_id),
CONSTRAINT PK_dis_user PRIMARY KEY (user_id, dis_id)
);
From SQLite Foreign Key Support/3. Required and Suggested Database Indexes:
Usually, the parent key of a foreign key constraint is the primary key of the parent table.
If they are not the primary key, then the parent key columns must be collectively
subject to a UNIQUE constraint or have a UNIQUE index.
With this:
CREATE TABLE user_disease (
...........................
med_id REFERENCES dis_med(medication_id),
...........................
);
the column med_id of user_disease references the column medication_id of dis_med, which is not the PRIMARY KEY of dis_med and there is no UNIQUE constraint for it. It just references med_id of medication .
Why do you need the column med_id in user_disease?
You have dis_id referencing disease, which may also be used to retrieve from dis_med (all) the row(s) from dis_med for that disease.
Checking if the following tables have a certain relationship among their records would be useful:
-- Table: privilege_group
CREATE TABLE privilege_group (
privilege_group_id integer NOT NULL CONSTRAINT privilege_group_pk PRIMARY KEY AUTOINCREMENT,
name text NOT NULL,
CONSTRAINT privilege_group_name UNIQUE (name)
);
-- Table: privilege_relationship
CREATE TABLE privilege_relationship (
privilege_relationship_id integer NOT NULL CONSTRAINT privilege_relationship_pk PRIMARY KEY AUTOINCREMENT,
parent_id integer NOT NULL,
child_id integer NOT NULL,
CONSTRAINT privilege_relationship_parent_child UNIQUE (parent_id, child_id),
CONSTRAINT privilege_relationship_parent_id FOREIGN KEY (parent_id)
REFERENCES privilege_group (privilege_group_id),
CONSTRAINT privilege_relationship_child_id FOREIGN KEY (child_id)
REFERENCES privilege_group (privilege_group_id),
CONSTRAINT privilege_relationship_check CHECK (parent_id != child_id)
);
Parents can have many children, children can have many parents. Writing code to process records outside of the database is always possible, but is it possible to use a depth-first (or breadth-first) search to check if a child has a particular parent?
My related question received a comment from CL. that mentions the WITH clause, but my experience with hierarchical queries is rather limited and insufficient to understand, select, and apply the examples on the page to my goal:
Only worked with hierarchical queries in Oracle.
Only used to implement "range" number generators (like in Python).
Only seen how to process records in a broad-to-narrow pattern.
Not sure if an expanding result set in a hierarchical query is possible.
Unsure of how to select a depth-first or breadth-first search strategy.
Could someone show me how to find out if a child has a parent if the names of both are known?
This is a standard tree search (using UNION instead of UNION ALL to prevent infinite loops):
WITH RECURSIVE ParentsOfG1(id) AS (
SELECT privilege_group_id
FROM privilege_group
WHERE name = 'G1'
UNION
SELECT parent_id
FROM privilege_relationship
JOIN ParentsOfG1 ON id = child_id
)
SELECT id
FROM ParentsOfG1
WHERE id = (SELECT privilege_group_id
FROM privilege_group
WHERE name = 'P2');
Depth/breadth-first does not matter for this.
An alternative to CL.'s answer could be this query which has been reformatted and adjusted to use bound parameters that could be plugged into a project that needs to check certain relationships:
WITH RECURSIVE parent_of_child(id)
AS (
SELECT privilege_group_id
FROM privilege_group
WHERE name = :child
UNION
SELECT parent_id
FROM privilege_relationship
JOIN parent_of_child
ON id = child_id)
SELECT id
FROM parent_of_child
WHERE id = (
SELECT privilege_group_id
FROM privilege_group
WHERE name = :parent)
I already checked out this question, and thought I had the answer - but then it didn't look right to me.
I have the following pared down example:
CREATE TABLE pipelines (
name VARCHAR NOT NULL,
owner VARCHAR NOT NULL,
description VARCHAR,
PRIMARY KEY (name, owner),
FOREIGN KEY(owner) REFERENCES user (id)
);
CREATE TABLE tasks (
id INTEGER NOT NULL,
title VARCHAR,
pipeline VARCHAR,
owner VARCHAR,
PRIMARY KEY (id),
FOREIGN KEY(pipeline) REFERENCES pipelines (name),
FOREIGN KEY(owner) REFERENCES pipelines (owner)
);
CREATE TABLE user (
id VARCHAR NOT NULL,
name VARCHAR,
password VARCHAR,
PRIMARY KEY (id)
);
pragma foreign_keys=on;
insert into user values ('wayne', '', '');
insert into pipelines values ('pipey', 'wayne', '');
insert into tasks values (1, 'hello', 'pipey', 'wayne');
When executing this code, it bails out:
$ sqlite3 foo.sq3 '.read mismatch.sql'
Error: near line 27: foreign key mismatch
Through the list in the question I cited:
the parent table (user) exists.
the parent columns (name, owner) exist
the parent columns are, in fact, the primary key (I thought that may have been it originally)
the child table references all of the primary key columns in the parent table
So what in the world could be causing this error?
The documentation says:
Usually, the parent key of a foreign key constraint is the primary key of the parent table. If they are not the primary key, then the parent key columns must be collectively subject to a UNIQUE constraint or have a UNIQUE index.
In the pipelines table, neither the name nor the owner columns are, by themselves, unique.
I guess you actually want to have a two-column foreign key in the tasks table:
FOREIGN KEY(pipeline, owner) REFERENCES pipelines(name, owner)
Why am I getting a SQLite "foreign key mismatch" error when executing script below?
DELETE
FROM rlsconfig
WHERE importer_config_id=2 and
program_mode_config_id=1
Here is main table definition:
CREATE TABLE [RLSConfig] (
"rlsconfig_id" integer PRIMARY KEY AUTOINCREMENT NOT NULL,
"importer_config_id" integer NOT NULL,
"program_mode_config_id" integer NOT NULL,
"l2_channel_config_id" integer NOT NULL,
"rls_fixed_width" integer NOT NULL
,
FOREIGN KEY ([importer_config_id])
REFERENCES [ImporterConfig]([importer_config_id]),
FOREIGN KEY ([program_mode_config_id])
REFERENCES [ImporterConfig]([importer_config_id]),
FOREIGN KEY ([importer_config_id])
REFERENCES [ImporterConfig]([program_mode_config_id]),
FOREIGN KEY ([program_mode_config_id])
REFERENCES [ImporterConfig]([program_mode_config_id])
)
and referenced table:
CREATE TABLE [ImporterConfig] (
"importer_config_id" integer NOT NULL,
"program_mode_config_id" integer NOT NULL,
"selected" integer NOT NULL DEFAULT 0,
"combined_config_id" integer NOT NULL,
"description" varchar(50) NOT NULL COLLATE NOCASE,
"date_created" datetime NOT NULL DEFAULT (CURRENT_TIMESTAMP),
PRIMARY KEY ([program_mode_config_id], [importer_config_id])
,
FOREIGN KEY ([program_mode_config_id])
REFERENCES [ProgramModeConfig]([program_mode_config_id])
)
When you use a foreign key over a table that has a composite primary key you must use a composite foreign key with all the fields that are in the primary key of the referenced table.
Example:
CREATE TABLE IF NOT EXISTS parents
(
key1 INTEGER NOT NULL,
key2 INTEGER NOT NULL,
not_key INTEGER DEFAULT 0,
PRIMARY KEY ( key1, key2 )
);
CREATE TABLE IF NOT EXISTS childs
(
child_key INTEGER NOT NULL,
parentKey1 INTEGER NOT NULL,
parentKey2 INTEGER NOT NULL,
some_data INTEGER,
PRIMARY KEY ( child_key ),
FOREIGN KEY ( parentKey1, parentKey2 ) REFERENCES parents( key1, key2 )
);
I am not sure about SQLite. But I found this link on google. http://www.sqlite.org/foreignkeys.html.
Some of the reasons can be
The parent table does not exist, or
The parent key columns named in the foreign key constraint do not exist, or
The parent key columns named in the foreign key constraint are not the primary key of the parent table and are not subject to a unique constraint using collating sequence specified in the CREATE TABLE, or
The child table references the primary key of the parent without specifying the primary key columns and the number of primary key columns in the parent do not match the number of child key columns.
Unfortunately, SQLite gives this error all the time without mentioning WHICH foreign key constraint failed. You are left to try to check them one by one, which often doesn't work, and then rebuild the table without the constraints and add them back one by one until you find the problem. SQLite is great in a lot of ways, but this isn't one of them.