I have String column in clickhouse table.
I try alter table with modify type to UInt32:
ALTER TABLE main.abonents
MODIFY COLUMN
device_type UInt32 DEFAULT 0
but have error:
Received exception from server:
Code: 6. DB::Exception: Received from 5.200.55.122:9000. DB::Exception: Cannot parse string 'mo' as UInt32: syntax error at begin of string. Note: there are toUInt32OrZero function, which returns zero instead of throwing exception..
It's clear, clickhouse use toUint32 function on string like 'mobile' and throw exception. And its advice to use function toUInt32OrZero to convert type.
How can i use toUInt32OrZero function with ALTER TABLE??
There's no such way (as far as I know).
You can achieve it with a second table. Let's create one:
CREATE TABLE main.abonents_new AS main.abonents;
Then we have to alter column in that new table.
This table has no data yet, so it won't raise exceptions:
ALTER TABLE main.abonents_new MODIFY COLUMN device_type UInt32 DEFAULT 0;
Then, make sure no new data is written to main.abonents. We'd like to keep everything in place when we'll transfer the data to the new table.
Insert the data using INSERT INTO SELECT query. Make sure to list all the fields with the same order; wrap device_type to the converter function (toUInt32OrZero) :
INSERT INTO main.abonents_new SELECT field1, field2, ..., toUInt32OrZero(device_type) AS device_type, ..., fieldN FROM main.abonents;
Then, make sure that everything's alright (that rows count is the same, device_type was converted as intended, etc), then rename the tables:
RENAME TABLE main.abonents TO main.abonents_old;
RENAME TABLE main.abonents_new TO main.abonents;
(or, you may DROP the older table instead; although I'd keep the old data to be able to restore if things'd go south)
Related
I am trying to replace all of the NULL values to 0 in a column of a big table in HIVE.
However, every time I try to implement some code I end up generating a new column to the table. The column I am trying to change/modify still exists and still has the NULL values but the new column that is automatically generated (i.e. _c1) is what I want the column I am trying to modify, to look like.
I tried to run a COALESCE but that also ended up generating a new column. I also tried to implement a CASE WHEN, but the same results ensued.
Select *,
CASE WHEN columnname IS NULL THEN 0
ELSE columnname
END
from tablename;
Also tried
SELECT coalesce(columnname, CAST(0 AS BIGINT)) FROM tablename
I would just like to update the table with the other columns being as is but the column I want to modify still has its original name but instead of NULL values it has 0's that replaced them.
I don't want to generate a new column but modify an existing one.
How should I do that?
Use insert overwrite .. option.
insert overwrite table tablename
select c1,c2,...,coalesce(columnname,0) as columnname
from tablename
Note that you have to specify all the other column names required in select.
I want to write a function that returns table records that I can show in my app's grid. My app shall be oblivious to the table's structure. I want it to be still working when someone adds columns to the table or removes them.
In my app it shall look something like this:
myQuery = "select * from table(myfunction)";
...
The function should hence be something like:
CREATE OR REPLACE FUNCTION myfunction RETURN TABLE OF mytable%ROWTYPE AS ...
But RETURN TABLE OF mytable%ROWTYPE is not allowed. One has to create an SQL type.
But CREATE TYPE table_of_mytable_rows IS TABLE OF mytable%ROWTYPE is not allowed either.
So, is there a way to achieve exactly what I want?
As an alternative I thought of working with IDs. This would make my app's code look something like this:
myQuery = "select * from mytable where rowid in (select * from table(myfunction))";
...
And the function would then be
CREATE OR REPLACE FUNCTION myfunction RETURN TABLE OF UROWID AS ...
But again, RETURN TABLE OF UROWID is not allowed. Neither is creating the SQL table type with CREATE TYPE table_of_rowids IS TABLE OF UROWID.
I know I could create an object type resembling the table's primary key columns and then create a table type on this object. Then my app would have to know the table's primary key in order to
myQuery = "select * from mytable where (key1, key2) in (select key1, key2 from table(myfunction))";
...
I would much prefer my function to return table rows or rowids. Is this possible?
I'm currently still working on Oracle 11.2, but I would also be interested in solutions for newer versions.
I'm completely new to Hive and Stack Overflow. I'm trying to create a table with complex data type "STRUCT" and then populate it using INSERT INTO TABLE in Hive.
I'm using the following code:
CREATE TABLE struct_test
(
address STRUCT<
houseno: STRING
,streetname: STRING
,town: STRING
,postcode: STRING
>
);
INSERT INTO TABLE struct_test
SELECT NAMED_STRUCT('123', 'GoldStreet', London', W1a9JF') AS address
FROM dummy_table
LIMIT 1;
I get the following error:
Error while compiling statement: FAILED: semanticException [Error
10044]: Cannot insert into target because column number type are
different 'struct_test': Cannot convert column 0 from struct to
array>.
I was able to use similar code with success to create and populate a data type Array but am having difficulty with Struct. I've tried lots of code examples I've found online but none of them seem to work for me... I would really appreciate some help on this as I've been stuck on it for quite a while now! Thanks.
your sql error. you should use sql:
INSERT INTO TABLE struct_test
SELECT NAMED_STRUCT('houseno','123','streetname','GoldStreet', 'town','London', 'postcode','W1a9JF') AS address
FROM dummy_table LIMIT 1;
You can not insert complex data type directly in Hive.For inserting structs you have function named_struct. You need to create a dummy table with data that you want to be inserted in Structs column of desired table.
Like in your case create a dummy table
CREATE TABLE DUMMY ( houseno: STRING
,streetname: STRING
,town: STRING
,postcode: STRING);
Then to insert in desired table do
INSERT INTO struct_test SELECT named_struct('houseno',houseno,'streetname'
,streetname,'town',town,'postcode',postcode) from dummy;
No need to create any dummy table : just use command :
insert into struct_test
select named_struct("houseno","house_number","streetname","xxxy","town","town_name","postcode","postcode_name");
is Possible:
you must give the columns names in sentence from dummy or other table.
INSERT INTO TABLE struct_test
SELECT NAMED_STRUCT('houseno','123','streetname','GoldStreet', 'town','London', 'postcode','W1a9JF') AS address
FROM dummy
Or
INSERT INTO TABLE struct_test
SELECT NAMED_STRUCT('houseno',tb.col1,'streetname',tb.col2, 'town',tb.col3, 'postcode',tb.col4) AS address
FROM table1 as tb
CREATE TABLE IF NOT EXISTS sunil_table(
id INT,
name STRING,
address STRUCT<state:STRING,city:STRING,pincode:INT>)
ROW FORMAT DELIMITED
FIELDS TERMINATED BY '.';
INSERT INTO sunil_table 1,"name" SELECT named_struct(
"state","haryana","city","fbd","pincode",4500);???
how to insert both (normal and complex)data into table
I need to migrate table's column to another data type with some modifications. Given: table 'USER' with column 'ORDER_TIME' (DateTime format). It's required to change column type to NUMBER, convert that time to a minutes (e.g. 8:00 AM = 480 mins.) and to store new value. As i understand, i need to create new column with required NUMBER data type, iterate over all records, do some recalculations, store new value, drop old column and rename new one to an actual name. So, basically, algorithm is:
ALTER TABLE USER ADD ORDER_TIME_MINS NUMBER(4) NULL;
iteration and recalculation
ALTER TABLE USER
DROP COLUMN ORDER_TIME
RENAME COLUMN ORDER_TIME_MINS TO ORDER_TIME;
Can you suggest me some reading on how that iteration may looks like?
You can try like this:
update tablename
set columnName = to_number(to_char(to_date(yourDateColumn,'hh24:mi:ss'),'sssss'))/60
And if your time is in format 08:00 PM then like
update tablename
set columnName =TO_NUMBER(TO_CHAR(TO_DATE('08:00 AM','HH:MI AM'),'SSSSS'))/60
Rest of the steps which you have shown ie, dropping and renamin are fine.
I am unable to append data to tables that contain an array column using insert into statements; the data type is array < varchar(200) >
Using jodbc I am unable to insert values into an array column by values like :
INSERT INTO demo.table (codes) VALUES (['a','b']);
does not recognises the "[" or "{" signs.
Using the array function like ...
INSERT INTO demo.table (codes) VALUES (array('a','b'));
I get the following error using array function:
Unable to create temp file for insert values Expression of type TOK_FUNCTION not supported in insert/values
Tried the workaround...
INSERT into demo.table (codes) select array('a','b');
unsuccessfully:
Failed to recognize predicate '<EOF>'. Failed rule: 'regularBody' in statement
How can I load array data into columns using jdbc ?
My Table has two columns: a STRING, b ARRAY<STRING>.
When I use #Kishore Kumar Suthar's method, I got this:
FAILED: ParseException line 1:33 cannot recognize input near '(' 'a' ',' in statement
But I find another way, and it works for me:
INSERT INTO test.table
SELECT "test1", ARRAY("123", "456", "789")
FROM dummy LIMIT 1;
dummy is any table which has atleast one row.
make a dummy table which has atleast one row.
INSERT INTO demo.table (codes) VALUES (array('a','b')) from dummy limit 1;
hive> select codes demo.table;
OK
["a","b"]
Time taken: 0.088 seconds, Fetched: 1 row(s)
Suppose I have a table employee containing the fields ID and Name.
I create another table employee_address with fields ID and Address. Address is a complex data of type array(string).
Here is how I can insert values into it:
insert into table employee_address select 1, 'Mark', 'Evans', ARRAY('NewYork','11th
avenue') from employee limit 1;
Here the table employee just acts as a dummy table. No data is copied from it. Its schema may not match employee_address. It doesn't matter.