I have the following hsqldb table, in which I map UUIDs to auto incremented IDs:
SHORT_ID (BIG INT, PK, auto incremented) | UUID (VARCHAR, unique)
Create command:
CREATE TABLE mytable (SHORT_ID BIGINT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY, UUID VARCHAR(36) UNIQUE)
In order to add new pairs concurrently, I want to use the atomic MERGE INTO statement. So my (prepared) statement looks like this:
MERGE INTO mytable USING (VALUES(CAST(? AS VARCHAR(36)))) AS v(x) ON mytable.UUID = v.x WHEN NOT MATCHED THEN INSERT VALUES v.x
When I execute the statement (setting the placeholder correctly), I always get a
Caused by: org.hsqldb.HsqlException: row column count mismatch
Could you please give me a hint, what is going wrong here?
Thanks in advance.
Epilogue
I reported this behavior as a bug, and it is today (2010-05-25) fixed in the hsqldb SVN repository, per hsqldb-Bugs-2989597. (Thanks, hsqldb!)
Updated Answer
Neat one! Here's what I got to work under HSQLDB 2.0.0rc9, which supports the syntax and the error message you posted:
MERGE INTO mytable
USING (SELECT 'a uuid' FROM dual) AS v(x) -- my own "DUAL" table
ON (mytable.UUID = v.x)
WHEN NOT MATCHED THEN INSERT
VALUES (NULL, x) -- explicit NULL for "SHORT_ID" :(
Note, I could not convince 2.0.0rc9 to accept ... THEN INSERT (UUID) VALUES (x), which is IIUC a perfectly acceptable and clearer specification than the above. (My SQL knowledge is hardly compendious, but this looks like a bug to me.)
Original Answer
You appear to be INSERTing a single value (a 1-tuple) into a table with more than one column. Perhaps you can modify the end of your statement to read:
... WHEN NOT MATCHED INSERT ("UUID") VALUES (v.x)
I got same problems but solve in few minutes.
Its occur when datavalues and table structure are not same.Add explicit (NULL) in your empty column value.
Like i created table
TestCase table:
ID TESTCASEID DESCRIPTION
but your insertion statement you donot want to add any description for any testcase description then you have to explicite in insertion statement you have to set null value for description
Related
I'm inserting bulk records using COPY statement in PostgreSQL. What I realize is, the sequence IDs are not getting updated and when I try to insert a record later, it throws duplicate sequence ID. Should I manually update the sequence number to get the number of records after performing COPY? Isn't there a solution while performing COPY, just increment the sequence variable, that is, the primary key field of the table? Please clarify me on this. Thanks in advance!
For instance, if I insert 200 records, COPY does good and my table shows all the records. When I manually insert a record later, it says duplicate sequence ID error. It very well implies that it didn’t increment the sequence ids during COPYing as work fine during normal INSERTing. Instead of instructing the sequence id to set the max number of records, won’t there be any mechanism to educate the COPY command to increment the sequence IDs during its bulk COPYing option?
You ask:
Should I manually update the sequence number to get the number of records after performing COPY?
Yes, you should, as documented here:
Update the sequence value after a COPY FROM:
| BEGIN;
| COPY distributors FROM 'input_file';
| SELECT setval('serial', max(id)) FROM distributors;
| END;
You write:
it didn’t increment the sequence ids during COPYing as work fine during normal INSERTing
But that is not so! :) When you perform a normal INSERT, typically you do not specify an explicit value for the SEQUENCE-backed primary key. If you did, you would run in to the same problems as you are having now:
postgres=> create table uh_oh (id serial not null primary key, data char(1));
NOTICE: CREATE TABLE will create implicit sequence "uh_oh_id_seq" for serial column "uh_oh.id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "uh_oh_pkey" for table "uh_oh"
CREATE TABLE
postgres=> insert into uh_oh (id, data) values (1, 'x');
INSERT 0 1
postgres=> insert into uh_oh (data) values ('a');
ERROR: duplicate key value violates unique constraint "uh_oh_pkey"
DETAIL: Key (id)=(1) already exists.
Your COPY command, of course, is supplying an explicit id value, just like the example INSERT above.
I realize that this is a bit old but maybe someone might still be looking for the answer.
As other said COPY works in a similar way as INSERT, so for inserting into a table that has a sequence, you simply don't mention the sequence field at all and it is taken care of for you. For COPY it works in the same exact way. But doesn't it COPY require ALL fields in the table to be present in the text file? The correct answer is NO, it doesn't, but it is the default behavior.
To COPY and leave the sequence out do the following:
COPY $YOURSCHEMA.$YOURTABLE(col1,col2,col3,col4) FROM '$your_input_file' DELIMITER ',' CSV HEADER;
No need to manually update the schema afterwards, it works as intended and in my testing is just about as fast.
You could copy to a sister table, then insert into mytable select * from sister - that would increment the sequence.
If your loaded data has the id field, don't select it for the insert: insert into mytable (col1, col2, col3) select col1, col2, col3 from sister
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.
Consider the following table:
create table language (
id integer generated always as identity (START WITH 1, INCREMENT BY 1),
name long varchar,
constraint language_pk primary key (id)
);
To which I'd insert an entry this way.
insert into language(name) values ('value');
How does one know what value for id was created? Just doing a SELECT using the name field is not valid, because there can be duplicate entries.
Through plain SQL:
insert into language(name) values ('value');
SELECT IDENTITY_VAL_LOCAL();
See the manual for details: http://db.apache.org/derby/docs/10.7/ref/rrefidentityvallocal.html
When doing this from a Java class (through JDBC) you can use getGeneratedKeys() after "requesting" them with the approriate executeUpdate() method.
You use the JDBC method
st.execute(sql, Statement.RETURN_GENERATED_KEYS);
ResultSet keys = st.getGeneratedKeys();
as documented in the Derby manual.
See also Javadocs: DatabaseMetaData#supportsGetGeneratedKeys()
and Statement#getGeneratedKeys()
You could execute this statement (NB, not 100% sure this syntax is correct for Derby:
SELECT TOP 1 id FROM language ORDER BY id DESC
To find the last inserted ID.
Alternative for Derby:
SELECT MAX(id) from language
Obviously this will only be accurate if no other inserts (including inserts by other users) have happened between your insert and select.
See also this discussion:
I've declared the following table for use by audit triggers:
CREATE TABLE audit_transaction_ids (id IDENTITY PRIMARY KEY, uuid VARCHAR UNIQUE NOT NULL, `time` TIMESTAMP NOT NULL);
The trigger will get invoked multiple times in the same transaction.
The first time the trigger is invoked, I want it to insert a new
row with the current TRANSACTION_ID() and time.
The subsequent times the trigger is invoked, I want it to return
the existing "id" (I invoke Statement.getGeneratedKeys() to that end)
without altering "uuid" or "time".
The current schema seems to have two problems.
When I invoke MERGE INTO audit_transaction_ids (uuid, time) KEY(id) VALUES(TRANSACTION_ID(), NOW()) I get: org.h2.jdbc.JdbcSQLException: Column "ID" contains null values; SQL
statement: MERGE INTO audit_transaction_ids (uuid, time) KEY(id) VALUES
(TRANSACTION_ID(), NOW()) [90081-155]
I suspect that invoking MERGE on an existing row will alter "time".
How do I fix both these problems?
MERGE is analogous to java.util.Map.put(key, value): it will insert the row if it doesn't exist, and update the row if it does. That being said, you can still merge into a table containing AUTO_INCREMENT columns so long as you use another column as the key.
Given customer[id identity, email varchar(30), count int] you could merge into customer(id, email, count) key(email) values((select max(id) from customer c2 where c2.email='test#acme.com'), 'test#acme.com', 10). Meaning, re-use the id if a record exists, use null otherwise.
See also https://stackoverflow.com/a/18819879/14731 for a portable way to insert-or-update depending on whether a row already exists.
1. MERGE INTO audit_transaction_ids (uuid, time) KEY(id) VALUES(TRANSACTION_ID(), NOW())
If you just want to insert a new row, use:
INSERT INTO audit_transaction_ids (uuid, time) VALUES(TRANSACTION_ID(), NOW())
MERGE without setting the value for the column ID doesn't make sense if ID is used as the key, because that way it could never (even in theory) update an existing rows. What you could do is using another key column (in the case above there is no column that could be used). See the documentation for MERGE for details.
2. Invoking MERGE on an existing row will alter "time"
I'm not sure if you talk about the fact that the value of the column 'time' is altered. This is the expected behavior if you use MERGE ... VALUES(.., NOW()), because the MERGE statement is supposed to update that column.
Or maybe you mean that older versions of H2 returned different values within the same transaction (unlike most other databases, which return the same value within the same transaction). This is true, however with H2 version 1.3.155 (2011-05-27) and later, this incompatibility is fixed. See also the change log: "CURRENT_TIMESTAMP() and so on now return the same value within a transaction." It looks like this is not the problem in your case, because you do seem to use version 1.3.155 (the error message [90081-155] includes the build / version number).
Short Answer:
MERGE INTO AUDIT_TRANSACTION_IDS (uuid, time) KEY (uuid, time)
VALUES (TRANSACTION_ID(), NOW());
little performance tip: make sure uuid is indexed
Long Answer:
MERGE is basically an UPDATE which INSERTs when no record found to be updated.
Wikipedia gives a more concise, standardized syntax of
MERGE but you have to supply your own update and insert.
(Whether this will be supported in H2 or not is not mine to answer)
So how do you update a record using MERGE in H2? You define a key to be looked up for, if it is found you update the row (with column names you supply, and you can define DEFAULT here, to reset your columns to its defaults), otherwise you insert the row.
Now what is Null? Null means unknown, not found, undefined, anything which is not what you're looking for.
That is why Null works as key to be looked up for. Because it means the record is not found.
MERGE INTO table1 (id, col1, col2)
KEY(id) VALUES (Null, 1, 2)
Null has a value. it IS a value.
Now let's see your SQL.
MERGE INTO table1 (id, col1, col2)
KEY(id) VALUES (DEFAULT, 1, 2)
What is that implying? To me, it says
I have this [DEFAULT, 1, 2], find me a DEFAULT in column id,
then update col1 to 1, col2 to 2, if found.
otherwise, insert default to id, 1 to col1, 2 to col2.
See what I emphasized there? What does that even mean? What is DEFAULT? How do you compare DEFAULT to id?
DEFAULT is just a keyword.
You can do stuff like,
MERGE INTO table1 (id, col1,
timeStampCol) KEY(id) VALUES (Null, 1,
DEFAULT)
but don't put DEFAULT in the key column.
I have a postgres table like this:
CREATE SEQUENCE seq;
CREATE TABLE tbl (id INTEGER DEFAULT VALUE nextval('seq'), data VARCHAR);
When I insert into the table:
INSERT INTO tbl (data) VALUES ('something');
How can I get back the value of the id field for the record I just created?
(Note, I may have got some of the SQL syntax a bit off; the gist should be clear, though)
Suppose for the sake of argument that I'm not able to call currval on the same session because I don't control the transaction boundaries. I might be working in the same session with my next call, but I might not be, too.
You're looking for INSERT ... RETURNING. From The Manual's section on INSERT:
The optional RETURNING clause causes INSERT to compute and return value(s) based on each row actually inserted. 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. The syntax of the RETURNING list is identical to that of the output list of SELECT.
In the same session:
SELECT currval('seq');
EDIT: But if you can't use currval/nextval because you don't know if the inserting and selecting of the sequence value will occur in the same session, and if you're on postgresql 8.2 or later, you could probably write your insert statement like this.
INSERT INTO tbl (data) VALUES ('something') RETURNING id;
which should also return the last inserted id.
Use nextval and currval, take a look here: http://www.postgresql.org/docs/8.0/static/functions-sequence.html