For example, if column1 has a bunch of descriptions and multiple NULLs, and I want to replace each NULL with a unique description.
using a COALESCE function I can do
COALESCE(Column1,'Description')
and this will replace every NULL in the column with "description", how can I adress each NULL individually and not replace all of them with the same value?
You have to decide first you are replacing the nulls based on what criteria.Then you can use CASE to decide individual description for each criteria or condition.
Here below i have taken the criteria of Row number
WITH data
AS (SELECT NULL id
FROM dual
UNION ALL
SELECT NULL
FROM dual),
d1
AS (SELECT ROWNUM rw,
d.*
FROM data d)
SELECT CASE
WHEN rw = 1 THEN COALESCE(id, 'star')
ELSE COALESCE(id, 'moon')
END AS id
FROM d1;
Related
I'm trying to take value from a non-empty row and overwrite it in the subsequent rows until another non-empty row appears and then write that in the subsequent rows. Coming from ABAP Background, I'm not sure how to accomplish this in HANA SQL Script. Here's a picture to show what the data looks like.
Basically 'Doe, John' should be overwritten into all the empty rows until 'Doe, Jane' appears and then 'Doe, Jane' should be overwritten into empty rows until another name appears.
My idea is to store the non-empty row in a local variable, but I haven't had much success so far. Here's my code:
tempTab1 = SELECT
CASE WHEN EMPLOYEE <> ''
THEN lv_emp = EMPLOYEE
ELSE EMPLOYEE
END AS EMPLOYEE,
FROM :tempTab;
In general, rows in dataset are unordered until you explicitly specify ORDER BY part of SQL. If you observe some order it may be a side-effect and can vary. So first of all you have to explicitly create a row number column (assume it's name is RECORD).
Then you should go this way:
Select only rows with non-empty data in column.
Use LEAD(RECORD) over(order by RECORD) to identify the next non-empty record number.
Join your source dataset to dataset defined on step 3 on between condition for RECORD field.
with a as (
select 1 as record, 'Val1' as field1 from dummy union
select 2 as record, '' as field1 from dummy union
select 3 as record, '' as field1 from dummy union
select 4 as record, 'Val2' as field1 from dummy union
select 5 as record, '' as field1 from dummy union
select 6 as record, '' from dummy union
select 7 as record, '' from dummy union
select 8 as record, 'Val3' as field1 from dummy
)
, fill_base as (
select field1, record, lead(record, 1, record) over(order by record asc) as next_record
from a
where field1 <> '' and field1 is not null
)
select
a.record
, case
when a.field1 = '' or a.field1 is null
then f.field1
else a.field1
end as field1
, a.field1 as field1_original
from a
left join fill_base as f
on a.record > f.record
and a.record < f.next_record
The performance in HANA may be bad in some cases since it process window functions very bad.
Here is another more elegant solution with two nested window functions than does not force you to write multiple selects for each column: How to make LAG() ignore NULLS in SQL Server?
You can use window aggregate function LAST_VALUE to achieve the imputation of missing values.
Sample Data
CREATE TABLE sample (id integer, sort integer, value varchar(10));
INSERT INTO sample VALUES (4711, 1, 'Hello');
INSERT INTO sample VALUES (4712, 2, null);
INSERT INTO sample VALUES (4713, 3, null);
INSERT INTO sample VALUES (4714, 4, 'World');
INSERT INTO sample VALUES (4715, 5, null);
INSERT INTO sample VALUES (4716, 6, '!');
Generate a new column with imputed values
SELECT base.*, LAST_VALUE(fill.value ORDER BY fill.sort) AS value_imputed
FROM sample base
LEFT JOIN sample fill ON fill.sort <= base.sort AND fill.value IS NOT NULL
GROUP BY base.id, base.sort, base.value
ORDER BY base.id, base.sort
Result
Note that sort could be anything determining the order (e.g. a timestamp).
WITH group1 AS
(
SELECT
[column1],
[column2]
FROM
table1
),
Group2 AS
(
SELECT
(column3),
COUNT(column3)
FROM
table 2 AS Count
WHERE
(year (date_value) = 2018 and month(Date_vaLue) = 2)
GROUP BY
column2
)
SELECT *
FROM group1
JOIN group2 ON group1. table1 = group2.table2;
I get an error:
No column name was specified for column 2 of 'group2'
As this isn't a column and is just an identifier I am confused why it thinks the code (Group2 AS (Select (column3 ),) is a column.
I am new at sql so this might just be a silly error
Column 1 is a name and column two is a unique key for that name
Column 2 and column 3 contain the same exact data and I am simply trying to show the number of times it occurs in the DB on the column 3 table, including 0, and relate it back to column 1.
Each datapoint in column 3 contains only data from column2.
Thanks in advance!
There are so many errors in that query, I don't know where to start
In a cte each column must have a name. select columnname makes the resulting column named columnname. An aggregation function like count does not set a column name, so your second column in your second cte does not have a name, as the error states. Use
SELECT column, count(othercolumn) AS ctcol ...
You can't add columns you don't use in the grouping to your select list without an aggregation function. Furthermore you can't add a column aggregated and unggregated to the select list. But I suppose, that's only a typo
SELECT column2, COUNT(column3) AS ctcol
FROM tablexy
...
GROUP BY column2
Your cte don't have any columns named table1 or table2, so your join won't work. Use column named from the cte
SELECT * FROM group1 JOIN group2 ON group1.column2 = group2.column2
I think you need to name the column COUNT(column3) , so...
Group2 AS (Select (column3 ),
COUNT (column3) as cntr
From table 2 as Count
Where (year (date_value) = 2018 and month(Date_vaLue) = 2)
Group by column2
)
I have a table in MS Access with rows which have a column called "repeat"
I want to SELECT all the rows, duplicated by their "repeat" column value.
For example, if repeat is 4, then I should return 4 rows of the same values. If repeat is 1, then I should return only one row.
This is very similar to this answer:
https://stackoverflow.com/a/6608143
Except I need a solution for MS Access.
First create a "Numbers" table and fill it with numbers from 1 to 1000 (or up to whatever value the "Repeat" column can have):
CREATE TABLE Numbers
( i INT NOT NULL PRIMARY KEY
) ;
INSERT INTO Numbers
(i)
VALUES
(1), (2), ..., (1000) ;
then you can use this:
SELECT t.*
FROM TableX AS t
JOIN
Numbers AS n
ON n.i <= t.repeat ;
If repeat has only small values you can try:
select id, col1 from table where repeat > 0
union all
select id, col1 from table where repeat > 1
union all
select id, col1 from table where repeat > 2
union all
select id, col1 from table where repeat > 3
union all ....
What you can do is to retrieve the one 'unique' row and copy this row/column into a string however many copies you need from it using a for loop.
I have a quite unique need to make select always return one row
My SQL:
select * from table1 Where (table1.pk = :p1) or (table1.fk1 = :p1)
The above SQL always has two cases for return:
1- my Select return two records:
The only different is one of the records has data while the other has only the ID filled with data while the rest of its fields are null. I need in this case to return only the one that has data in other fields.
2- my Select return one record
In this case the record returned has only the ID field filled with data while the rest of the fields are null however this is what I want and no need for any further processing.
Please advise if is it possible to do that in one plain Select SQL. I can not use stored procedure.
You can use the first clause of the select statement to get only 1 row.
Given your specific conditions, you can order the result set descending by the rest of the fields to be sure the null row is selected only in case there's no data row (null goes first in firebird 2.5, but AFAIK this changed somewhere in the last versions, so check your specific version before applying this).
Your final query will look like this:
select first 1 *
from table1
where (table1.pk = :p1)
or (table1.fk1 = :p1)
order by somecolumn;
somecolumn being the most relevant of the other fields that can contain null values.
you can test this with this statements:
--two rows, one with ID and values and the other with ID and null
with q1 as (
select 1 id, 'data' othercolumn
from rdb$database
union
select 2 id, null othercolumn
from rdb$database
)
select first 1 *
from q1
order by othercolumn nulls last;
--versus:
--onw row with ID and null
with q1 as (
select 2 id, null othercolumn
from rdb$database
)
select first 1 *
from q1
order by othercolumn nulls last;
Let's say I have a boolean field in a database table and I want to get a tally of how many are 1 and how many are 0. Currently I am doing:
SELECT 'yes' AS result, COUNT( * ) AS num
FROM `table`
WHERE field = 1
UNION
SELECT 'no' AS result, COUNT( * ) AS num
FROM `table`
WHERE field = 0;
Is there an easier way to get the result so that even if there are no false values I will still get:
----------
|yes | 3 |
|no | 0 |
----------
One way would be to outer join onto a lookup table. So, create a lookup table that maps field values to names:
create table field_lookup (
field int,
description varchar(3)
)
and populate it
insert into field_lookup values (0, 'no')
insert into field_lookup values (1, 'yes')
now the next bit depends on your SQL vendor, the following has some Sybase (or SQL Server) specific bits (the outer join syntax and isnull to convert nulls to zero):
select description, isnull(num,0)
from (select field, count(*) num from `table` group by field) d, field_lookup fl
where d.field =* fl.field
you are on the right track, but the first answer will not be correct. Here is a solution that will give you Yes and No even if there is no "No" in the table:
SELECT 'Yes', (SELECT COUNT(*) FROM Tablename WHERE Field <> 0)
UNION ALL
SELECT 'No', (SELECT COUNT(*) FROM tablename WHERE Field = 0)
Be aware that I've checked Yes as <> 0 because some front end systems that uses SQL Server as backend server, uses -1 and 1 as yes.
Regards
Arild
This will result in two columns:
SELECT SUM(field) AS yes, COUNT(*) - SUM(field) AS no FROM table
Because there aren't any existing values for false, if you want to see a summary value for it - you need to LEFT JOIN to a table or derived table/inline view that does. Assuming there's no TYPE_CODES table to lookup the values, use:
SELECT x.desc_value AS result,
COALESCE(COUNT(t.field), 0) AS num
FROM (SELECT 1 AS value, 'yes' AS desc_value
UNION ALL
SELECT 2, 'no') x
LEFT JOIN TABLE t ON t.field = x.value
GROUP BY x.desc_value
SELECT COUNT(*) count, field FROM table GROUP BY field;
Not exactly same output format, but it's the same data you get back.
If one of them has none, you won't get that rows back, but that should be easy enough to check for in your code.