I've got a set of staging tables where I accept data, scrub, and cleanse them before inserting to the target table. The target table has a primary key constraint and what I'm inserting is a primary key.
I check for the absence of the primary key in the target table before I insert. I insert only records that ARE NOT in the target table, based on the primary key's absence:
INSERT INTO Target
SELECT
primKey
, user_state
, test_state
FROM
myStagingTable3
By this point, the stagingTable3 has only data that are NOT present in the Target Table using the following where clause:
WHERE
primKey not in (Select primKey from Target)
Somehow, I'm getting a primary key violation error :
Msg 2627, Level 14, State 1. (procedure failed at line #...)
Violation of Primary Key constraint 'pk1101AE.' Cannot insert
duplicate key in object 'Target'
My questions:
under what conditions could a primary key violation occur when the
key that I want to insert is NOT present in the target table?
could a prior delete of records cause the primary key to be retained? If so,
can I work around this somehow?
something else?
It's pretty clear that my staging tables have the key and that the Target table does not. Yet the insert fails.
This happens because your staging table contains multiple rows with the same value of primKey.
If it does not matter to you which {user_state, test_state} pair among the duplicated ones makes it into the insert, you can bypass the issue entirely by adding a simple group by, like this:
INSERT INTO Target
(SELECT
primKey
, MAX(user_state)
, MAX(test_state)
FROM
myStagingTable3
GROUP BY primKey)
Related
CREATE TABLE IF NOT EXISTS students (
student_id INT,
name VARCHAR(24),
major VARCHAR(24),
PRIMARY KEY(student_id)
);
SELECT * FROM student;
INSERT INTO students VALUES(1,'Jack','Biology');
You're specifying the primary key (student_id) and from the error it already exists. You have a few options:
Don't specify the primary key. It should be set to autoincrement anyway, assuming that this is the primary table that students are entered into, and from the name of the table (students) it seems like it is. Then the query will be:
INSERT INTO students VALUES('Jack','Biology');
and then the table will autoincrement the primary key to the next pointer.
Use INSERT IGNORE. This will silently fail if you try to insert a student ID that already exists (or on any query that violates unique keys).
INSERT IGNORE INTO students VALUES(1, 'Jack','Biology');
This will not cause table changes, but it will also not cause an error that interrupts the script, and it will insert any rows that don't fail, say if you had multiple values inserted. The plain INSERT will fail for the entire list, not just the erroneous value.
Use ON DUPLICATE KEY UPDATE. This will update a list of values if it encounters a duplicate key.
INSERT INTO students VALUES(1, 'Jack','Biology')
ON DUPLICATE KEY UPDATE name = values(name), major = values(major);
In this case, you will change the values in the table that match the key. In this case, whichever student is student_id 1 will have its name and major updated to the supplied values. For instance, let's say that Jack changed his major to Chemistry. This would update student_id 1 to Jack, Chemistry and reflect his new major.
Use REPLACE INTO. I avoid this one. It is similar to ON DUPLICATE KEY UPDATE, but it removes the old entry and replaces it with a new one with a new ID. This can cause you problems with foreign keys, and also if you have a small primary key and you constantly replace into it, you can end up with a primary id that's bigger than the limits you set.
Well, your student_id is primary key, clearly that table is already exist with some data with student_id=1 hence you cannot insert another row with the same primary key value.
I have a database assignment where I must build the following database.
The issue is, I am given a table to create called dependent which has 5 columns. 1 of these columns is dependent_name. It can't be a Foreign Key because there is not table for the dependents, so I assume it is suppose to be a Primary Key.
When I attempted to add the data in the table I was given an error that says I cannot have duplicate values for primary key.
Of course this is because you cannot have duplicate primary keys ( Alice is a duplicate value in this situation ), but I am not sure how to get around this. I guess I could make another table called dependent_info and make the dependent_name and FK, but this is not stated in the instructions from the teacher.
Is there something I am missing here?
I´m creating a database addrees and I want to know what I need to set in Mysql to don´t store repeat values?
Like
Addrees 1 ("teste",1,new york,eua);
Addrees 2 ("teste",1,new york,eua);
If this happen my database will not store.
So what I need to do?
To alter an already existing table, run this MySQL command:
alter table yourtablename add unique index(firstcolumn, secondcolumn, thirdcolumn, fourthcolumn);
That'll add the unique constraint to the specified columns. Here's how to specify such a constraint in the CREATE TABLE.
CREATE TABLE buyers (
buyer_id INT UNSIGNED NOT NULL,
first_name CHAR(19) NOT NULL,
last_name CHAR(19) NOT NULL,
age SMALLINT NOT NULL,
post_code SMALLINT NOT NULL,
UNIQUE idx_flname_age (first_name,last_name,age)
);
The primary key constraint will do this too, as mentioned by #Ajeesh
EDIT:
As per the suggestion in the comment, if you want to avoid errors generated by this unique constraint, you have three good options:
INSERT IGNORE
and
INSERT...ON DUPLICATE KEY UPDATE
and
REPLACE
INSERT IGNORE will not do anything if the insert violates the unique constraint, except log a harmless warning. The table will be left as is, and no error would be reported. This may be desireable in some cases.
More commonly is the second option, ON DUPLICATE KEY UPDATE, which says "Well, if the key already exists, then update that key's row like this instead."
And lastly is REPLACE, which will, if the key already exists, delete the row, then do an INSERT as normal. If the key did not exist previously, it will simply act as an INSERT.
This stack overflow answer has some examples.
"INSERT IGNORE" vs "INSERT ... ON DUPLICATE KEY UPDATE"
You need to call these fields a UNIQUE_KEY
To make a column to be distinct you need to have Primary Key constraint/Unique Key. Primary key is used for relating one table with another and it's values should not be NULL. But in your case you can have Unique constraint to store only unique/distinct values.
I have a table set up on a mysql database called "access" with three columns called:
rights_id, (PRIMARY KEY)
username,
name,
In the rights_id column the user can only input 3 different values ("1","2", or "3") 1 means resource, 2 means manager, and 3 means administrator. my problem occurs when there are more than one row with the same rights_id (ie: more than one administrator).It displays an error that tells me i can't have a duplicate entry for the PRIMARY KEY... i was wondering if there was a way to supress this error and allow me to do this? im using vb.net to interact with my MYSQL database running on a Windows 7 OS. Thanks!
rights_id is primary key. You can have only distinct values of primary keys in a table. So consider another primary key or do not use rights_id column this way. You should learn more about relational databases if you would like to use them.
In my opinion the best solution there is to add anothe column id which could be a primary key (you could also set multi-column primary key but this wouldn't fit your data in my opinion).
I'm not sure what "name" means in that table. If it's safe for me to ignore it . . .
If each username can have only one "rights_id", then the primary key should be username. If each username can have more than one "rights_id"--if user Catcall can have rights_id 1 and 2 at the same time--then your primary key should be the pair of columns (rights_id, username).
Since MySQL doesn't enforce CHECK constraints, you should have a separate table of rights id numbers, containing three rows.
create table rights_ids (
rights_id integer primary key
);
insert into rights_ids values (1);
insert into rights_ids values (2);
insert into rights_ids values (3);
Then you can set a foreign key constraint that will prevent any numbers besides those three from appearing in the table named "access". Something like
alter table access
add constraint foreign key (rights_id) references rights_ids (rights_id);
Create a compound PRIMARY KEY of rights_id and username (if usernames are unique that is).
No, you can't suppress that error. The issue is that rights_id is NOT your primary key.
The primary key must be able to uniquely identify a row in your table. If you can have more than 1 rights_id entry, then that is NOT able to fulfill the role of a primary key.
Read this wiki article about unique keys (a primary key is a specific type of unique key).
As Shef pointed out, you'll likely want to use a compound primary key of rights_id and username if that combination actually uniquely identifies a single row in the table.
I have a table with a unique key for two columns:
CREATE TABLE `xpo`.`user_permanent_gift` (
`id` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
`fb_user_id` INT UNSIGNED NOT NULL ,
`gift_id` INT UNSIGNED NOT NULL ,
`purchase_timestamp` TIMESTAMP NULL DEFAULT now() ,
PRIMARY KEY (`id`) ,
UNIQUE INDEX `user_gift_UNIQUE` (`fb_user_id` ASC, `gift_id` ASC) );
I want to insert a row into that table, but if the key exists, to do nothing! I don't want an error to be generated because the keys exist.
I know that there is the following syntax:
INSERT ... ON DUPLICATE KEY UPDATE ...
but is there something like:
INSERT ... ON DUPLICATE KEY DO NOTHING
?
Yes, use INSERT ... ON DUPLICATE KEY UPDATE id=id (it won't trigger row update even though id is assigned to itself).
If you don't care about errors (conversion errors, foreign key errors) and autoincrement field exhaustion (it's incremented even if the row is not inserted due to duplicate key), then use INSERT IGNORE like this:
INSERT IGNORE INTO <table_name> (...) VALUES (...)
HOW TO IMPLEMENT 'insert if not exist'?
1. REPLACE INTO
pros:
simple.
cons:
too slow.
auto-increment key will CHANGE(increase by 1) if there is entry matches unique key or primary key, because it deletes the old entry then insert new one.
2. INSERT IGNORE
pros:
simple.
cons:
auto-increment key will not change if there is entry matches unique key or primary key but auto-increment index will increase by 1
some other errors/warnings will be ignored such as data conversion error.
3. INSERT ... ON DUPLICATE KEY UPDATE
pros:
you can easily implement 'save or update' function with this
cons:
looks relatively complex if you just want to insert not update.
auto-increment key will not change if there is entry matches unique key or primary key but auto-increment index will increase by 1
4. Any way to stop auto-increment key increasing if there is entry matches unique key or primary key?
As mentioned in the comment below by #toien: "auto-increment column will be effected depends on innodb_autoinc_lock_mode config after version 5.1" if you are using innodb as your engine, but this also effects concurrency, so it needs to be well considered before used. So far I'm not seeing any better solution.
Use ON DUPLICATE KEY UPDATE ...,
Negative : because the UPDATE uses resources for the second action.
Use INSERT IGNORE ...,
Negative : MySQL will not show any errors if something goes wrong, so you cannot handle the errors. Use it only if you don’t care about the query.