I need to make an sql query which tries to update a row by primary key and if it doesn't exist insert it. The solution needs to be universal for most databases (MySQL, H2, Postgres, Oracle, DB2, MSSQL, Hsql, Derby).
For code examples please consider a simple table consisting of two columns: id (Pr.Key) and txt
You want SQL's MERGE statement, but it doesn't work everywhere:
MERGE into thetable using (select theid from thetable)
when matched then update thetable thecolumn = thevalue where id = theid
when not matched then insert into thetable blablabla;
The other solution is to try and insert anyway, handle the error, detect whether it is a constraint violation and if so update instead.
You have to use a stored procedure to do this.
See : http://jumpingbean.co.za/blog/mysql-if-exists-update-else-insert
Maybe:
INSERT INTO table (id,txt) VALUES (1,"Hello")
ON DUPLICATE KEY UPDATE txt="World";
But this is MySQL only
Related
I want to insert a row if it doesn't already exist. If it does already exist, I want to get it's primary key.
Can this be done without using two queries, for instance using a UNIQUE constraint on the columns and ON CONFLICT ... TELL ME THE CONFLICTING ROWID?
Please note that I don't have experience with SQLite. However, after perusing the online documentation, I don't believe that it supports data-change table references, so no, this isn't possible.
My reccommendation is to write your INSERT in such a way that it won't fail if the row exists - it just won't insert a row. Something like this:
INSERT INTO destinationTable (colA, colB)
(SELECT :colAValue, :colBValue
WHERE NOT EXISTS (SELECT '1'
FROM destinationTable
WHERE uniqueColumn = :uniqueColumn))
This works because the selection won't return a row if it already exists. You can then either look at the return code/state to see if it INSERTed a row, or just SELECT with the unique column, to get the identity column.
DON'T rely on your constraint to catch this. Constraints are to catch application errors, and this is solely a business/implementation detail.
In a word, no. You can't, with SQLite, either INSERT data or, on some condition, SELECT it.
Other SQL engines might allow it, but SQLite can't.
What you can do is INSERT OR IGNORE, which will just not bring up an error. See http://sqlite.org/lang_conflict.html
I have inserted a row with some data in a table where a primary key is present. How would one "SELECT" the primary key of the row one just inserted?
I should have been more specific and mentioned that I'm currently
using SQLite.
For MS SQL Server:
SCOPE_IDENTITY() will return you the last generated identity value within your current scope:
SELECT SCOPE_IDENTITY() AS NewID
For SQL Server 2005 and up, and regardless of what type your primary key is, you could always use the OUTPUT clause to return the values inserted:
INSERT INTO dbo.YourTable(col1, col2, ...., colN)
OUTPUT Inserted.PrimaryKey
VALUES(val1, val2, ....., valN)
SQL Server:
You can use ##IDENTITY. After an insert statement, you can run:
select ##identity
This will give you the primary key of the record you just inserted. If you are planning to use it later, I suggest saving it:
set #MyIdentity = ##identity
If you are using this in a stored procedure and want to access it back in your application, make sure to have nocount off.
For MySQL, use LAST_INSERT_ID()
http://dev.mysql.com/doc/refman/5.0/en/getting-unique-id.html
You should also be able to start a transaction, insert the row, and select the row using some field that has a unique value that you just inserted, like a timestamp or guid. This should work in pretty much any RDBMS that supports transactions, as long as you have a good unique field to select the row with.
If you need to retrieve the new index in MS SQL when there are triggers on the table then you have to use a little workaround. A simple OUTPUT will not work. You have to do something like this (in VB.NET):
DECLARE #newKeyTbl TABLE (newKey INT);
INSERT INTO myDbName(myFieldName) OUTPUT INSERTED.myKeyName INTO #newKeyTbl VALUES('myValue'); " & _
SELECT newKey FROM #newKeyTbl;"
If using .NET, then the return value from this query can be directly cast to an integer (you have to call "ExecuteScalar" on the .NET SqlCommand to get the return).
For SQLite:
SELECT [Column_1], [Column_2],... [Column_n]
FROM [YourTable]
WHERE rowid = (SELECT last_insert_rowid())
whereas:
Column_1, Column_2,... Column_n: are the primary key of YourTable.
If you'd created YourTable with primary key replaced rowid (i.e. one column pk defined as INTEGER PRIMARY KEY) you just use:
SELECT last_insert_rowid()
Which is a common case.
Finally, this wont work for WITHOUT_ROWID tables.
Please Check:
https://www.sqlite.org/lang_corefunc.html#last_insert_rowid
For PostgreSQL,
INSERT INTO tablename (col1, col2, ...)
VALUES (val1, val2, ...)
RETURNING idcol;
The optional RETURNING clause causes INSERT to compute and return value(s) based on each row actually inserted (or updated, if an ON CONFLICT DO UPDATE clause was used). This is primarily useful for obtaining values that were supplied by defaults, such as a serial sequence number. However, any expression using the table's columns is allowed.
https://www.postgresql.org/docs/current/sql-insert.html
For Postgresql:
SELECT CURRVAL(pg_get_serial_sequence('schema.table','id'))
Source: PostgreSQL function for last inserted ID
select MAX(id_column) from table
That, in theory, should return you that last inserted id. If it's a busy database with many inserts going on it may not get the one you just did but another.
Anyhow, an alternative to other methods.
Can I do this in SQL 2005?
SELECT 'C'+inserted.exhid AS ExhId,inserted.exhname AS ExhName,inserted.exhid AS RefID INTO mytable FROM inserted
WHERE inserted.altname IS NOT NULL
It won't work if the table exists, but will create the table if it is non-existent. How do I get it to insert into an existing table?
like this
INSERT INTO mytable
SELECT 'C'+inserted.exhid AS ExhId,inserted.exhname AS ExhName,
inserted.exhid AS RefID FROM inserted
WHERE inserted.altname IS NOT NULL
you also don't need the aliases in this case
SQLMenace's answer is correct. But to add to it, I would suggest that it is a good practice to explicitly list your columns that you are inserting into in the event the table structure/column order ever changes, that way your proc stands a better change of working consistently.
INSERT INTO mytable (
ExhId,
ExhName,
RefID)
SELECT 'C'+inserted.exhid,
inserted.exhname,
inserted.exhid
FROM inserted
WHERE inserted.altname IS NOT NULL
To insert into an existing table, use INSERT INTO instead of `SELECT INTO
I need some SQL to update a record in a database if it exists and insert it when it does not, looking around there looks to be several solutions for this, but I don't know what are the correct/ accepted ways to do this.
I would ideally like it to work on both Firebird 2 and MySQL 5 as the update will need to be ran against both databases, and it would be simpler if the same SQL ran on both, if it worked on more database that would be a plus.
Speed and reliability also factor in, reliability over speed in this case but it will potentially be used to update 1000's of records in quick succession (over different tables).
any subjections?
In Firebird 2.1 you can use UPDATE OR INSERT for simple cases or MERGE for more complex scenarios.
You should either use something like this:
BEGIN TRANSACTION
IF EXISTS (SELECT * FROM the_table WHERE pk = 'whatever')
UPDATE the_table SET data = 'stuff' WHERE pk = 'whatever'
ELSE
INSERT INTO the_table (pk, data) VALUES ('whatever', 'stuff')
COMMIT
Or this, but send them separately and ignore any errors from the INSERT about violating primary key constraints:
INSERT INTO the_table (pk, data) VALUES ('whatever', 'stuff')
UPDATE the_table SET data = 'stuff' WHERE pk = 'whatever'
In firebird before 2.1 you can use this tricky way:
insert into table (id, a, b, c) values (:id, :a, :b, :c)
when SQLCODE -803
do
begin
update table set a = :a, b = :b, c = :c where id = :id;
end;
For MySQL, try the REPLACE command: http://dev.mysql.com/doc/refman/5.0/en/replace.html
(Please see the comment on this answer by Milan Babuskov for equivalents on Firebird.)
REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted.
Syntax :
REPLACE [LOW_PRIORITY | DELAYED]
[INTO] tbl_name [(col_name,...)]
{ VALUES | VALUE}
({expr | DEFAULT},...),(...),...
Whereas : It is best to avoid REPLACE when working with constraints.
I've used INSERT in MySQL to update rows with:
INSERT INTO table () VALUES () ON DUPLICATE KEY UPDATE key
But you can't use an auto generated key.
From my code (Java) I want to ensure that a row exists in the database (DB2) after my code is executed.
My code now does a select and if no result is returned it does an insert. I really don't like this code since it exposes me to concurrency issues when running in a multi-threaded environment.
What I would like to do is to put this logic in DB2 instead of in my Java code.
Does DB2 have an insert-or-update statement? Or anything like it that I can use?
For example:
insertupdate into mytable values ('myid')
Another way of doing it would probably be to always do the insert and catch "SQL-code -803 primary key already exists", but I would like to avoid that if possible.
Yes, DB2 has the MERGE statement, which will do an UPSERT (update or insert).
MERGE INTO target_table USING source_table ON match-condition
{WHEN [NOT] MATCHED
THEN [UPDATE SET ...|DELETE|INSERT VALUES ....|SIGNAL ...]}
[ELSE IGNORE]
See:
http://publib.boulder.ibm.com/infocenter/db2luw/v9/index.jsp?topic=/com.ibm.db2.udb.admin.doc/doc/r0010873.htm
https://www.ibm.com/support/knowledgecenter/en/SS6NHC/com.ibm.swg.im.dashdb.sql.ref.doc/doc/r0010873.html
https://www.ibm.com/developerworks/community/blogs/SQLTips4DB2LUW/entry/merge?lang=en
I found this thread because I really needed a one-liner for DB2 INSERT OR UPDATE.
The following syntax seems to work, without requiring a separate temp table.
It works by using VALUES() to create a table structure . The SELECT * seems surplus IMHO but without it I get syntax errors.
MERGE INTO mytable AS mt USING (
SELECT * FROM TABLE (
VALUES
(123, 'text')
)
) AS vt(id, val) ON (mt.id = vt.id)
WHEN MATCHED THEN
UPDATE SET val = vt.val
WHEN NOT MATCHED THEN
INSERT (id, val) VALUES (vt.id, vt.val)
;
if you have to insert more than one row, the VALUES part can be repeated without having to duplicate the rest.
VALUES
(123, 'text'),
(456, 'more')
The result is a single statement that can INSERT OR UPDATE one or many rows presumably as an atomic operation.
This response is to hopefully fully answer the query MrSimpleMind had in use-update-and-insert-in-same-query and to provide a working simple example of the DB2 MERGE statement with a scenario of inserting AND updating in one go (record with ID 2 is updated and record ID 3 inserted).
CREATE TABLE STAGE.TEST_TAB ( ID INTEGER, DATE DATE, STATUS VARCHAR(10) );
COMMIT;
INSERT INTO TEST_TAB VALUES (1, '2013-04-14', NULL), (2, '2013-04-15', NULL); COMMIT;
MERGE INTO TEST_TAB T USING (
SELECT
3 NEW_ID,
CURRENT_DATE NEW_DATE,
'NEW' NEW_STATUS
FROM
SYSIBM.DUAL
UNION ALL
SELECT
2 NEW_ID,
NULL NEW_DATE,
'OLD' NEW_STATUS
FROM
SYSIBM.DUAL
) AS S
ON
S.NEW_ID = T.ID
WHEN MATCHED THEN
UPDATE SET
(T.STATUS) = (S.NEW_STATUS)
WHEN NOT MATCHED THEN
INSERT
(T.ID, T.DATE, T.STATUS) VALUES (S.NEW_ID, S.NEW_DATE, S.NEW_STATUS);
COMMIT;
Another way is to execute this 2 queries. It's simpler than create a MERGE statement:
update TABLE_NAME set FIELD_NAME=xxxxx where MyID=XXX;
INSERT INTO TABLE_NAME (MyField1,MyField2) values (xxx,xxxxx)
WHERE NOT EXISTS(select 1 from TABLE_NAME where MyId=xxxx);
The first query just updateS the field you need, if the MyId exists.
The second insertS the row into db if MyId does not exist.
The result is that only one of the queries is executed in your db.
I started with hibernate project where hibernate allows you to saveOrUpdate().
I converted that project into JDBC project the problem was with save and update.
I wanted to save and update at the same time using JDBC.
So, I did some research and I came accross ON DUPLICATE KEY UPDATE :
String sql="Insert into tblstudent (firstName,lastName,gender) values (?,?,?)
ON DUPLICATE KEY UPDATE
firstName= VALUES(firstName),
lastName= VALUES(lastName),
gender= VALUES(gender)";
The issue with the above code was that it updated primary key twice which is true as
per mysql documentation:
The affected rows is just a return code. 1 row means you inserted, 2 means you updated, 0 means nothing happend.
I introduced id and increment it to 1. Now I was incrementing the value of id and not mysql.
String sql="Insert into tblstudent (id,firstName,lastName,gender) values (?,?,?)
ON DUPLICATE KEY UPDATE
id=id+1,
firstName= VALUES(firstName),
lastName= VALUES(lastName),
gender= VALUES(gender)";
The above code worked for me for both insert and update.
Hope it works for you as well.