From the documentation, you have to put a NOT NULL modifier in the column definition to mark it as such, just like for other SQL databases.
Consider this table:
CREATE TABLE test (
name String NOT NULL,
isodate DateTime('Europe/Berlin') NOT NULL
) ENGINE = MergeTree()
ORDER BY (isodate)
If I would try to insert NULL for both columns (or at least one), the expected behaviour is that Clickhouse declines insertion since the columns are marked as NOT NULL. Instead, Clickhouse creates a new row, where isodate is 1970-01-01 01:00:00 and name is an empty string, which are the default values for those data types apparently.
What do I have to do so that Clickhouse declines such inserts?
My Clickhouse server version is 21.12.3.
In ClickHouse, NULL and NOT NULL do change the behavior of the data type, but not in the way other relational databases - it is syntactically compatible with other relational database but not semantically (a Int32 NULL is the same as a Nullable(Int32), as a Int32 NOT NULL is the same as a Int32). A column defined as NOT NULL does not mean it will refuse to insert fields whose values are NULL in the insert statement - it means ClickHouse will use the default expression for the column type (or if it is not specified in the column definition, the default value for the data type). This behavior is expected in ClickHouse when input_format_null_as_default is enabled (the default for Clickhouse 21.12.3).
To throw exceptions for such invalid values you need to change the system setting input_format_null_as_default to 0. If you use clickhouse-client, you can disable it while connecting to clickhouse:
clickhouse-client -h ... --input_format_null_as_default 0
or after:
clickhouse> SET input_format_null_as_default=0
This way, a statement like insert into test (name, isodate) values (NULL, NULL); will behave more likely most relational databases.
Clickhouse behaviour with Not Null constraints is not compatible with other databases.
You can overcome it using check constraints https://clickhouse.com/docs/en/sql-reference/statements/create/table/#constraints
CREATE TABLE test (
name String NOT NULL,
isodate DateTime('Europe/Berlin') NOT NULL,
CONSTRAINT isodate_not_null CHECK isodate <> toDateTime(0, 'Europe/Berlin')
) ENGINE = MergeTree()
ORDER BY (isodate)
insert into test(name) values ('x');
DB::Exception: Constraint `isodate_not_null` for table default.test (f589312a-1592-426a-b589-312a1592b26a) is violated at row 1. Expression: (isodate != toDateTime(0)). Column values: isodate = 0. (VIOLATED_CONSTRAINT)
insert into test values ('x', now());
OK.
The reason is performance, in OLAP databases need to ingest data as fast as possible.
Related
I have an oracle table. Table's DDL is (not have the primary key)
create table CLIENT_ACCOUNT
(
CLIENT_ID VARCHAR2(18) default ' ' not null,
ACCOUNT_ID VARCHAR2(18) default ' ' not null,
......
)
create unique index UK_ACCOUNT
on CLIENT_ACCOUNT (CLIENT_ID, ACCOUNT_ID)
Then, the data's scale is very huge, maybe 100M records. I want to traverse this whole table's data with batch.
Now, I use the table's index to batch traverse. But I have some oracle grammar problems.
# I want to use this SQL, but grammar error.
# try to use b-tree's index to locate start position, but not work
select * from CLIENT_ACCOUNT
WHERE (CLIENT_ID, ACCOUNT_ID) > (1,2)
AND ROWNUM < 1000
ORDER BY CLIENT_ID, ACCOUNT_ID
Has the fastest way to batch touch table data?
Wild guess:
select * from CLIENT_ACCOUNT
WHERE CLIENT_ID > '1'
and ACCOUNT_ID > '2'
AND ROWNUM < 1000;
It would at least compile, although whether it correctly implements your business logic is a different matter. Note that I have cast your filter criteria to strings. This is because your columns have a string datatype and you are defaulting them to spaces, so there's a high probability those columns contain non-numeric values.
If this doesn't solve your problem, please edit your question with more details; sample input data and expected output is always helpful in these situations.
Your data model seems odd.
Your columns are defined as varchar2. So why is your criteria numeric?
Also, why do you default the key columns to space? It would be better to leave unpopulated values as null. (To be clear, NULL is not a good thing in an indexed column, it's just better than a space.)
I want to inserted into my collection some SQL records, but I can not. I'm a beginner. Can you help me ?
This is my tables :
CREATE TYPE article_type AS OBJECT (idA CHAR(10), nomA CHAR(10), prixA CHAR(10) )
CREATE TYPE facture_type AS OBJECT (idF CHAR(10), dateFact DATE)
CREATE TYPE ens_collection_fact AS OBJECT (refFact facture_type, refArticle article_type)
CREATE TYPE collection_fact AS TABLE OF ens_collection_fact
CREATE TYPE client_type AS OBJECT (idC NUMBER, nomC CHAR(10),adresse CHAR(10), Compose collection_fact )
CREATE TABLE Article OF article_type
CREATE TABLE Facture OF facture_type
CREATE TABLE Client OF client_type (PRIMARY KEY(idC)) NESTED TABLE Compose STORE AS temp
This is my query that I want to insert, but I have an error from the Oracle : ORA-02315
INSERT INTO ECOLER.CLIENT VALUES
(100, 'Jules Verne', '1', Collection_fact(Ens_collection_fact(reffact('A','2002-12-10'), ens_collection_fact(refarticle('D','E','F'))) ))
Thank in advance
reffact and refarticle are identifiers for objects within other objects, not types; you need to refer to the actual types. You also need to supply both values for each Ens_collection_fact attribute for the default constructor; you can pass null if you only want one or the other:
INSERT INTO CLIENT VALUES
(100, 'Jules Verne', '1',
Collection_fact(
Ens_collection_fact(facture_type('A',date '2002-12-10'), null),
Ens_collection_fact(null, article_type('D','E','F'))
)
)
Also notice that I've added the date keyword so it's providing an actual date literal rather than a string, which would be converted - if you're lucky - with your session NLS settings.
This will still error because 'Jules Verne' is 11 characters and you've defined the name attribute as 10 characters/bytes, but it will work with a shorter string literal.
db<>fiddle
I have Oracle database table with three columns i.e Id,RTOName,VehicleCode. my table looks like below
RTOName is the varchar2 type and VehicleCode is NUMBER(2,0) and is nullable field.
So I have the data like below and I want to fetch the records with Some VehicleCode and with null value. The table design like this already done so changing that will impact a lot in my application. I have a JPA Native Query that I used like this and I want to fetch the records with null values.
Query query = createNativeQuery("select RTOName,VehicleCode from tbl_vehiclecodes WHERE VehicleCode=#vCode");
query.setParameter("vCode", vehicleCode);
From above Query I will get only Non null valued record. Eg. for vCode parameter 61 I will get
Marathalli,61. If my vCode is null I have a problem and I wont get any record.
How to achieve this in Native Query?
I know that we can use IS NULL in the Query in where clause. Since I have some numbers here In my case how to solve this? Any help
Thanks
We can use OR here,
Following query will give you records with matched records for parameter vCode along with rows having null and in case of vCode is null you get the records only with null values.
Query query = createNativeQuery("select RTOName,VehicleCode from tbl_vehiclecodes WHERE (VehicleCode is null or VehicleCode=#vCode)");
Edit: considering the doubts from #Ranagal
If you want like in case of null value passed to vCode you want all the records having value in vehiclecode and also with null then we need to change the query like,
Query query = createNativeQuery("select RTOName,VehicleCode from tbl_vehiclecodes WHERE (VehicleCode is null or VehicleCode=coalesce(#vCode,VehicleCode))");
Does CockroachDB support default values for columns in its tables? Does it allow default values to be function values (e.g. current_date())?
You can set DEFAULT values using the DEFAULT constraint, which CockroachDB has documented here.
It also supports setting the default value as a function, e.g. to insert the date that a write occurred.
You would create a table with such a default column like:
CREATE TABLE purchase_log (
id INT PRIMARY KEY,
date_purchased DATE DEFAULT current_date()
);
Then all inserts to the table that don't specify the date_purchased column will have the column automatically populated with the return value of current_date() at the time of the insert.
why I am getting this error ?
In the table DDL I only have 2 columns , id (number) and name (varchar)
ALTER TABLE mytable ADD SUSPEND date NOT NULL
ORA-01758: table must be empty to add mandatory (NOT NULL) column
ORA-06512: at line 7
ORA-01758: table must be empty to add mandatory (NOT NULL) column ORA-06512: at line 7
And is your table empty? I think not.
There's probably a way around this involving adding the column as nullable, then populating every row with a non-NULL value, the altering the column to be not null.
Alternatively, since the problem is that these current rows will be given NULL as a default value, and the column is not allowed to be NULL, you can also get around it with a default value. From the Oracle docs:
However, a column with a NOT NULL constraint can be added to an existing table if you give a default value; otherwise, an exception is thrown when the ALTER TABLE statement is executed.
Here is a fiddle, how you could do it
Would a date in the future be acceptable as a temporary default? If so, this would work:
ALTER TABLE MYTABLE ADD (SUSPEND_DATE DATE DEFAULT(TO_DATE('21000101', 'YYYYMMDD'))
CONSTRAINT SUSPEND_DATE_NOT_NULL NOT NULL);
If table already contain the records then table won't allowes to add "Not null" column.
If you need same then set default value for the column or truncate the table then try.