In a sqlite3 database I would like to create a trigger on a view so that I can insert data over the view. Inside the trigger I would like to insert something in the tblmedia table. The id of the inserted row should be now also inserted into the tblbook as id.
In sqlite there are no variables. Otherwise I would store the returning value in the variable and would use it in the second query.
Can this even be achieved in sqlite?
Following my sql schema:
CREATE TABLE tblmedia(
id INTEGER PRIMARY KEY NOT NULL,
title VARCHAR NOT NULL,
raiting INTEGER,
file_name VARCHAR NOT NULL,
media_type TEXT NOT NULL
);
CREATE TABLE tblbook(
id INTEGER PRIMARY KEY NOT NULL,
author VARCHAR,
FOREIGN KEY (id) REFERENCES tblmedia(id) ON DELETE CASCADE
);
CREATE VIEW book AS
SELECT
m.id as id,
m.title as title,
b.author as author,
m.raiting as raiting,
m.file_name as file_name
FROM tblbook b
LEFT JOIN tblmedia m ON m.id = b.id;
CREATE TRIGGER insert_book
INSTEAD OF INSERT ON book
BEGIN
INSERT INTO tblmedia(title, raiting, file_name)
VALUES(new.title, new.raiting, new.file_name);
INSERT INTO tblbook(id, author)
VALUES (xx, new.author); -- xx should be the id from the previous insert
END
I have a database which contains many tables and these tables can be added or removedd any time.So I give each of them a different name like Table1,Table2,...
but it's uncomfortable to use these table because sometime I forget what infomation was stored in Table1
So I want something to differentiate these all tables, some property that I can be specified when I create a table and I can use to access a specific table when I need to fetch informations from that table
As one comment says, you could create a table for notes on the other tables:
CREATE TABLE notes (
id INT AUTO_INCREMENT,
table_name VARCHAR(64),
note VARCHAR(255),
PRIMARY KEY (id)
);
By the way, MySQL (but not SQLite) allows comments on the table itself:
CREATE TABLE table1 (
id INT AUTO_INCREMENT,
val INT,
PRIMARY KEY (id)
) COMMENT = 'Table of stuff';
-- Show the comment
SHOW TABLE STATUS WHERE NAME='table1';
-- Just show names and comments
SELECT `TABLE_NAME`, `TABLE_COMMENT`
FROM information_schema.tables
WHERE table_schema = DATABASE();
I have a trigger I'm writing whereby , once I delete a row, I want to delete the corresponding row in the another table (which is common_cis.security_function ).
and the source table is party.security_function
Here are the columns in common_cis.security_function :
URL
SCRTY_FUNC_NAME
SCRTY_FUNC_DESC
IDN
CREATE_TMSTMP
CNCRCY_USER_IDN
Here are the columns in party.security_function :
UPDATE_USER_SRC_SYS_CD
UPDATE_USER_ID
UPDATE_TS
SCRT_FUNC_NM
SCRT_FUNC_DESC
CREAT_USER_SRC_SYS_CD
CREAT_USER_ID
CREAT_TS
What I have so far is :
delete from common_cis.security_function CCSF
where CCSF.SCRTY_FUNC_NAME = :new.SCRT_FUNC_NM;
Is this the right idea? Or do I use some kind of row-ID ?
thanks
I think you should use integrity constraints for that, namely foreign key constraint with "ON DELETE CASCADE" condition.
Here is an example, but check first is there tables in your schema with names that I used:
-- create tables:
create table master_table(
URL varchar2(1000),
SCRTY_FUNC_NAME varchar2(100),
SCRTY_FUNC_DESC varchar2(1000));
create table detail_table(
SCRT_FUNC_NM varchar2(100),
SCRT_FUNC_DESC varchar2(1000),
UPDATE_USER_ID number,
UPDATE_TS varchar2(100));
-- add primary key and foreign key constraints:
alter table master_table add constraint function_pk primary key (SCRTY_FUNC_NAME);
alter table detail_table add constraint function_fk foreign key (SCRT_FUNC_NM) references master_table (SCRTY_FUNC_NAME) on delete cascade;
-- fill tables with data:
insert into master_table
values ('url number 1', 'sec function #1', 'description of function #1');
insert into detail_table
values('sec function #1', 'description', 1, '123abc');
insert into detail_table
values('sec function #1', 'description', 2, '456xyz');
-- check tables: first contains 1 row and second - 2 rows
select count(*) from master_table;
select count(*) from detail_table;
-- delete rows from first table only:
delete from master_table;
-- check tables once again - both are empty:
select count(*) from master_table;
select count(*) from detail_table;
-- clear test tables:
drop table detail_table;
drop table master_table;
I've found a few "would be" solutions for the classic "How do I insert a new record or update one if it already exists" but I cannot get any of them to work in SQLite.
I have a table defined as follows:
CREATE TABLE Book
ID INTEGER PRIMARY KEY AUTOINCREMENT,
Name VARCHAR(60) UNIQUE,
TypeID INTEGER,
Level INTEGER,
Seen INTEGER
What I want to do is add a record with a unique Name. If the Name already exists, I want to modify the fields.
Can somebody tell me how to do this please?
Have a look at http://sqlite.org/lang_conflict.html.
You want something like:
insert or replace into Book (ID, Name, TypeID, Level, Seen) values
((select ID from Book where Name = "SearchName"), "SearchName", ...);
Note that any field not in the insert list will be set to NULL if the row already exists in the table. This is why there's a subselect for the ID column: In the replacement case the statement would set it to NULL and then a fresh ID would be allocated.
This approach can also be used if you want to leave particular field values alone if the row in the replacement case but set the field to NULL in the insert case.
For example, assuming you want to leave Seen alone:
insert or replace into Book (ID, Name, TypeID, Level, Seen) values (
(select ID from Book where Name = "SearchName"),
"SearchName",
5,
6,
(select Seen from Book where Name = "SearchName"));
You should use the INSERT OR IGNORE command followed by an UPDATE command:
In the following example name is a primary key:
INSERT OR IGNORE INTO my_table (name, age) VALUES ('Karen', 34)
UPDATE my_table SET age = 34 WHERE name='Karen'
The first command will insert the record. If the record exists, it will ignore the error caused by the conflict with an existing primary key.
The second command will update the record (which now definitely exists)
You need to set a constraint on the table to trigger a "conflict" which you then resolve by doing a replace:
CREATE TABLE data (id INTEGER PRIMARY KEY, event_id INTEGER, track_id INTEGER, value REAL);
CREATE UNIQUE INDEX data_idx ON data(event_id, track_id);
Then you can issue:
INSERT OR REPLACE INTO data VALUES (NULL, 1, 2, 3);
INSERT OR REPLACE INTO data VALUES (NULL, 2, 2, 3);
INSERT OR REPLACE INTO data VALUES (NULL, 1, 2, 5);
The "SELECT * FROM data" will give you:
2|2|2|3.0
3|1|2|5.0
Note that the data.id is "3" and not "1" because REPLACE does a DELETE and INSERT, not an UPDATE. This also means that you must ensure that you define all necessary columns or you will get unexpected NULL values.
INSERT OR REPLACE will replace the other fields to default value.
sqlite> CREATE TABLE Book (
ID INTEGER PRIMARY KEY AUTOINCREMENT,
Name TEXT,
TypeID INTEGER,
Level INTEGER,
Seen INTEGER
);
sqlite> INSERT INTO Book VALUES (1001, 'C++', 10, 10, 0);
sqlite> SELECT * FROM Book;
1001|C++|10|10|0
sqlite> INSERT OR REPLACE INTO Book(ID, Name) VALUES(1001, 'SQLite');
sqlite> SELECT * FROM Book;
1001|SQLite|||
If you want to preserve the other field
Method 1
sqlite> SELECT * FROM Book;
1001|C++|10|10|0
sqlite> INSERT OR IGNORE INTO Book(ID) VALUES(1001);
sqlite> UPDATE Book SET Name='SQLite' WHERE ID=1001;
sqlite> SELECT * FROM Book;
1001|SQLite|10|10|0
Method 2
Using UPSERT (syntax was added to SQLite with version 3.24.0 (2018-06-04))
INSERT INTO Book (ID, Name)
VALUES (1001, 'SQLite')
ON CONFLICT (ID) DO
UPDATE SET Name=excluded.Name;
The excluded. prefix equal to the value in VALUES ('SQLite').
Firstly update it. If affected row count = 0 then insert it. Its the easiest and suitable for all RDBMS.
Upsert is what you want. UPSERT syntax was added to SQLite with version 3.24.0 (2018-06-04).
CREATE TABLE phonebook2(
name TEXT PRIMARY KEY,
phonenumber TEXT,
validDate DATE
);
INSERT INTO phonebook2(name,phonenumber,validDate)
VALUES('Alice','704-555-1212','2018-05-08')
ON CONFLICT(name) DO UPDATE SET
phonenumber=excluded.phonenumber,
validDate=excluded.validDate
WHERE excluded.validDate>phonebook2.validDate;
Be warned that at this point the actual word "UPSERT" is not part of the upsert syntax.
The correct syntax is
INSERT INTO ... ON CONFLICT(...) DO UPDATE SET...
and if you are doing INSERT INTO SELECT ... your select needs at least WHERE true to solve parser ambiguity about the token ON with the join syntax.
Be warned that INSERT OR REPLACE... will delete the record before inserting a new one if it has to replace, which could be bad if you have foreign key cascades or other delete triggers.
If you have no primary key, You can insert if not exist, then do an update. The table must contain at least one entry before using this.
INSERT INTO Test
(id, name)
SELECT
101 as id,
'Bob' as name
FROM Test
WHERE NOT EXISTS(SELECT * FROM Test WHERE id = 101 and name = 'Bob') LIMIT 1;
Update Test SET id='101' WHERE name='Bob';
I believe you want UPSERT.
"INSERT OR REPLACE" without the additional trickery in that answer will reset any fields you don't specify to NULL or other default value. (This behavior of INSERT OR REPLACE is unlike UPDATE; it's exactly like INSERT, because it actually is INSERT; however if what you wanted is UPDATE-if-exists you probably want the UPDATE semantics and will be unpleasantly surprised by the actual result.)
The trickery from the suggested UPSERT implementation is basically to use INSERT OR REPLACE, but specify all fields, using embedded SELECT clauses to retrieve the current value for fields you don't want to change.
I think it's worth pointing out that there can be some unexpected behaviour here if you don't thoroughly understand how PRIMARY KEY and UNIQUE interact.
As an example, if you want to insert a record only if the NAME field isn't currently taken, and if it is, you want a constraint exception to fire to tell you, then INSERT OR REPLACE will not throw and exception and instead will resolve the UNIQUE constraint itself by replacing the conflicting record (the existing record with the same NAME). Gaspard's demonstrates this really well in his answer above.
If you want a constraint exception to fire, you have to use an INSERT statement, and rely on a separate UPDATE command to update the record once you know the name isn't taken.
I can't add a not null constraint or remove a default constraint. I would like to add a datetime column to a table and have all the values set to anything (perhaps 1970 or year 2000) but it seems like i cant use not null without a default and I cant remove a default once added in. So how can i add this column? (once again just a plain datetime not null)
Instead of using ALTER TABLE ADD COLUMN, create a new table that has the extra column, and copy your old data. This will free you from the restrictions of ALTER TABLE and let you have a NOT NULL constraint without a default value.
ALTER TABLE YourTable RENAME TO OldTable;
CREATE TABLE YourTable (/* old cols */, NewColumn DATETIME NOT NULL);
INSERT INTO YourTable SELECT *, '2000-01-01 00:00:00' FROM OldTable;
DROP TABLE OldTable;
Edit: The official SQLite documentation for ALTER TABLE now warns against the above procedure because it “might corrupt references to that table in triggers, views, and foreign key constraints.” The safe alternative is to use a temporary name for the new table, like this:
CREATE TABLE NewTable (/* old cols */, NewColumn DATETIME NOT NULL);
INSERT INTO NewTable SELECT *, '2000-01-01 00:00:00' FROM YourTable;
DROP TABLE YourTable;
ALTER TABLE NewTable RENAME TO YourTable;