I have a table with 30+ rows and i want to do a select * however i also want to make sure that no rows containing null values are returned for a certain column. How can i do this without having to list each of the column names in the select?
My current SQL looks like this;
select *
from table
where (select column
from table
where column is not null) is > 20
However this does not work as the nested select returns more than one value.
Any suggestions please?
select * from table where column is not null
maybe?
SELECT *
FROM table
WHERE column > 20
Is that sufficient?
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 tried with following queries, these queries giving only the count of null values, What i need was to do a null check and return the column name.
select count(*)-count(columnA), count(*)-count(columnB) from table;
select count(*) from table where columnA is null;
You can also do
SELECT
SUM(IF(columnA is NULL,1,0)) as canulls,
SUM(IF(columnB is NULL,1,0)) as cbnulls
FROM table;
This will also give you the number of null fields for each columns.
I have a table which has around 30 columns.Out of 30 columns i need to retrieve around 25 column names where value is set to some specified value(say 1).
I am not able to find a way to do this.Will multiple if statement work as below
select if columnname1='1' then 'columnname1' else null
if columnname2='1' then 'columnname2' else null from table.
In case the value is not set to 1, i don't want to retrieve the column names.
The below query can give me the column names but i can't specify the value with below query
select DISTINCT COLUMN_NAME from ALL_TAB_COLUMNS where TABLE_NAME='table_name'.
Does this work for you?
SELECT COLUMN_NAME
from ALL_TAB_COLUMNS
where TABLE_NAME='TABLE_NAME'
AND INSTR(column_name,'1') >0
I have a table in oracle db which has a unique index composed of two columns (id and valid_from). The column valid_from is of type timestamps with time zone.
When I query the SYS.USER_IND_COLUMNS to see which columns my table is using as unique index, I can not see the name of the valid_from column but instead I see smth like SYS_NC00027$.
Is there any possibility that I can display the name valid_from rather than SYS_NC00027$. ?
Apparently Oracle creates a function based index for timestamp with time zone columns.
The definition of them can be found in the view ALL_IND_EXPRESSIONS
Something like this should get you started:
select ic.index_name,
ic.column_name,
ie.column_expression
from all_ind_columns ic
left join all_ind_expressions ie
on ie.index_owner = ic.index_owner
and ie.index_name = ic.index_name
and ie.column_position = ic.column_position
where ic.table_name = 'FOO';
Unfortunately column_expression is a (deprecated) LONG column and cannot easily be used in a coalesce() or nvl() function.
Use the below to verify the col info.
select column_name,virtual_column,hidden_column,data_default from user_tab_cols where table_name='EMP';
I have 2 tables that are the same structure. One is a temp one and the other is a prod one. The entire data set gets loaded each time and sometimes this dataset will have deleted records from the prior datasets. I load the dataset into temp table first and if any records were deleted I want to deleted them from the prod table also.
So how can I find the records that exist in prod but not in temp? I tried outer join but it doesn't seem to be working. It's returning all the records from the table in the left or right depending on doing left or right outer join.
I then also want to delete those records in the prod table.
One way would be to use the MINUS operator
SELECT * FROM table1
MINUS
SELECT * FROM table2
will show all the rows in table1 that do not have an exact match in table2 (you can obviously specify a smaller column list if you are only interested in determining whether a particular key exists in both tables).
Another would be to use a NOT EXISTS
SELECT *
FROM table1 t1
WHERE NOT EXISTS( SELECT 1
FROM table2 t2
WHERE t1.some_key = t2.some_key )
How about something like:
SELECT * FROM ProdTable WHERE ID NOT IN
(select ID from TempTable);
It'd work the same as a DELETE statement as well:
DELETE FROM ProdTable WHERE ID NOT IN
(select ID from TempTable);
MINUS can work here
The following statement combines results with the MINUS operator, which returns only rows returned by the first query but not by the second:
SELECT * FROM prod
MINUS
SELECT * FROM temp;
Minus will only work if the table structure is same