Is it possible to copy data from column A to column B for all records in a table in SQL?
How about this
UPDATE table SET columnB = columnA;
This will update every row.
UPDATE table_name SET
destination_column_name=orig_column_name
WHERE condition_if_necessary
This will update all the rows in that columns if safe mode is not enabled.
UPDATE table SET columnB = columnA;
If safe mode is enabled then you will need to use a where clause.
I use primary key as greater than 0 basically all will be updated
UPDATE table SET columnB = columnA where table.column>0;
If you want to copy a column to another column with a different data type in PostgresSQL, you must cast/convert to the data type first, otherwise it will return
Query 1 ERROR: ERROR: column "test_date" is of type timestamp without
time zone but expression is of type character varying LINE 1: update
table_name set test_date = date_string_col
^ HINT: You will need to rewrite or cast the expression.
An example of converting varchar to timestamp:
update table_name set timestamp_col = date_string_col::TIMESTAMP;
An example of converting varchar to int:
update table_name set int_column = string_col::INTEGER;
but any column type(except file or the similar) can be copied to string(character varying) without cast the type.
Related
I am creating a temp table in sybase like below
select col1 = null, col2 =2 into #myTable
Here when I try to update col1
update #myTable set col1 = 'test'
I get error - "[Error Code: 257, SQL State: 42000] Implicit conversion from datatype 'VARCHAR' to 'INT' is not allowed. Use the CONVERT function to run this query."
Can anyone please help me fix it?
Assuming this is Sybase ASE (257 is a standard ASE system error number) ...
col1=null doesn't tell the database what the datatype of col1 should be so the database defaults the column's datatype to int.
When creating a table via select/into you need to insure each column is created with the desired datatype. For this particular instance try:
select col1=convert(varchar(10),null), col2=convert(tinyint,2) into #myTable
NOTES:
modify the convert() calls to reference the desired datatypes
when the new column is populated from another table's column(s) the source column(s) datatypes will be used in determing the datatype of the new column
Also keep in mind the following:
select col1='test' into #otherTable
The datatype for col1 will be determined from the initial data value; in this case the value 'test' tells the database you need to store 4 characters so the database will default the column's datatype to varchar(4). This should be fine as long as you never intend to insert anything longer than varchar(4) otherwise you'll need to provide a convert() with the initial select/into to explicitly state the column's datatype, eg:
select col1=convert(varchar(35),'test') into #otherTable
Assuming you get past the Implicit conversion from datatype 'VARCHAR' to 'INT' is not allowed. error message your next bump-in-the road may occur if you try something like:
update #myTable set col2 = NULL
With the result being that you're presented with an error message similar to column does not allow nulls.
As with datatype determination, Sybase (ASE) will try to determine a column's NULLability in a few different ways:
if column is assigned a 'value' of NULL (as in the example: col1 = null) then ASE will configure the column to allow NULLs
if the column's value is being copied from another table then the source column's NULLability will be used in determining the new column's NULLability
if the query explicitly defines the column as NULLable (see example - below) then the column will be configured to allow NULLs
if the database option allow nulls by default is false (ASE default setting) then the column's NULLability will be set to 'not NULL'
when all else fails ...
if the database option allow nulls by default is true then the column's NULLability will be set to 'NULL'(able)
An example of explicitly defining the column to allow NULLs:
select col1 = convert(varchar(35) null,'test') into #otherTable
I am reading a flat file in hive and i have null values coming in file like below
a|b|null|null|d
and when I create table on top of this with below datatypes
a char(1),b char(1),c char(1),varchar2(2),char(1)
and the value in table coming like this
a,b,n,nu,d
The oneway I can do this is to make the datatype as varchar2(4) and add check at null.
But is there any other way i can do this.
SerDe treats 'null' strings as normal values, no difference between value 'a' and 'null'.
Try to add 'serialization.null.format'='null' property to your table definition:
ALTER TABLE mytable SET tblproperties('serialization.null.format'='null');
Another approach is to use STRING data type and case statements is select:
select case when col = 'null' then null end as col
...
I have a question related to the conversion of varchar to datetime.
This topic was covered already in the thread
SQL Server Convert Varchar to Datetime
but I would like to advance it bit further.
I have performed BULK INSERT into predefined tables where VARCHAR(255)
is the destination. I have a table dbo.USR_02_ALL_RAW and the field GLTGB which
holds strings in the following format: 07/16/2016.
I can convert it as a single string by the following code:
DECLARE #Date varchar(255)
set #Date= '07/16/2016'
SELECT CONVERT(datetime,RIGHT(#Date,4)+LEFT(#Date,2)+SUBSTRING(#Date,4,2))
and it gives me a result:
2016-07-16 00:00:00.000
However I would like to pass to the code the whole field GLTGB from the table
dbo.USR_02_ALL_RAW, convert it from VARCHAR into DATETIME and update the field GLTGB with these results.(converting the whole field from varchar to datetime)
Thank you!
First clear this, you want to Bulk insert or Bulk update. Since you already have a column GLTGB. If you want to update the value only.
update tab set GLTGB =
CONVERT(datetime,RIGHT(GLTGB,4)+LEFT(GLTGB,2)+SUBSTRING(GLTGB,4,2))
Or
If you want to update the field from varchar to datetime. Then process is little bit lengthy.
Alter table tab add newcol datetime --- Add new datetime type column
update tab set newcol =
CONVERT(datetime,RIGHT(GLTGB,4)+LEFT(GLTGB,2)+SUBSTRING(GLTGB,4,2)) --- update value in new column
Alter table tab drop column GLTGB --- drop GLGTB column
Alter table tab add GLGTB datetime --- add GLGTB column as datetime type
update tab set GLGTB = newcol --- update value from GLGTB from newcol
Alter table tab drop column newcol ---- remove unnecessary newcol
If you convert a value to datetime, then update the same database column it came from with the value then, since that column is still varchar, SQL will have to convert the value back to varchar again in order to store it. So you can't achieve anything useful with that kind of simple approach.
f you want to actually change the data type of the column, and also convert all the values, then I think you need to go through the following process:
1) Create a new varchar column in your table (which will be temporary)
2) copy all the data values from the GLTGB column into the new column (using an UPDATE statement)
3) Drop the GLTGB column
4) Re-create it with the same name but with datetime type
5) Use an UPDATE statement to re-populate the new GLTGB column from your temporary column
6) Finally, drop the temporary column
There may be a simpler way but that seems like the obvious process.
You can use the following code for updating but before that, you need to change the data type of your field to DateTime
update dbo.USR_02_ALL_RAW
set GLTGB=cast(CONVERT(datetime,RIGHT(#Date,4)+LEFT(#Date,2)+SUBSTRING(#Date,4,2)) as datetime)
I have a SQL Server database and I've changed my mind and instead of a column in my table being set as an int, I want to change it to a varchar. So I changed the type to varchar(8), and saved my changes in SQL Server Management Studio tool (V17.0).
It looks like the tool converted the int values to varchars when I saved the changes. I want to change the value of '1' to 'External', '2' to 'SPTR' and '3' to 'Other'. I was going to do one value at a time.
This is the simple SQL statement I tried:
UPDATE mytable
SET mycolumn = 'External'
WHERE mycolumn = '1'
The error message I get from SSMS is
Conversion failed when converting the varchar value 'External' to data type int"
It's as if the database thinks the type is int, but it's not, it's varchar(8).
Sounds like you really haven't changed the data type. This should resolve the problem.
ALTER TABLE mytable ALTER COLUMN mycolumn varchar(8);
GO
UPDATE mytable
SET mycolumn = CASE mycolumn WHEN '1' THEN 'External'
WHEN '2' THEN 'SPTR'
ELSE 'OTHER'
END;
Note, as well, you can update every value at the same time by using a CASE expression. Likely far easier than 3 UPDATE statements.
ALTER TABLE mytable ALTER COLUMN mycolumn varchar(50);
SELECT DATALENGTH ('External')
returns 8
As long as I know varchar does not use all 50 bytes, it only uses 8 in your case to store "External" field, why don't you try to change table size.
If you have changed mycolumn to a string, then the following should work:
UPDATE mytable
SET mycolumn = 'External'
WHERE mycolumn = '1';
If you are getting a type conversion error, then I assume you have a trigger on the table that is causing the problem. You might be wrong in saying that the type has changed. But even if you are correct, a trigger could still generate this issue.
I am trying to update the dbo.sysusers table so that the sid matches the dbo.syslogins table but I am getting error:
Disallowed implicit conversion from data type varchar to data type varbinary, table 'CallingCard.dbo.sysusers', column 'sid'. Use the CONVERT function to run this query.
My syntax for the update is:
UPDATE CallingCard.dbo.sysusers
SET sid = '0xDF5B9900C8FCAE438B0F4177B5'
WHERE uid = 6
I don't know how to update a varbinary column. How do i fix this?