Is it possible to structure a query that will display a static value for a row based on a column?
EG.
In INFORMIX, the syscolumns type is returned as an integer. I would like to have it print out the table type as a string rather than an integer.
For example, when I run a simple query to get the system tables
SELECT * FROM SYSCOLUMNS WHERE TABID < 100
I get
colname tabid colno coltype collength
------------------------------------------------
tabname 1 1 13 128
WHERE coltype = 13 corresponds to VARCHAR
So my original query would give me
COLNAME COLTYPE
col1 0
col2 1
...
But I want it to be returned as
COLNAME COLTYPE
col1 CHAR
col2 SMALLINT
...
Is such a thing possible to do in a single query?
SELECT COLUMN,
CASE
WHEN COLTYPE = 0 THEN 'CHAR'
WHEN COLTYPE = 1 THEN 'SMALLINT'
ELSE CAST(COLTYPE AS VARCHAR)
END as COLTYPE
FROM MyTable
So, for example, with this table:
COLUMN | COLTYPE
-------------+--------------
col1 | 0
col2 | 1
col3 | 2
The result would be:
COLUMN | COLTYPE
-------------+--------------
col1 | CHAR
col2 | SMALLINT
col3 | 2
However, if coltype maps to an id or similar in another table, it would make more sense to join to that table, like:
SELECT MyTable.COLUMN, SecondTable.COLUMNNAME
FROM MyTable
JOIN SecondTable ON MyTable.COLTYPE = SecondTable.COLTYPE
Related
I have a table
----------------------
| Col1 | Col2 | Col3 |
----------------------
| 1 |text1 | 1 |
----------------------
| 98 |text2 | 2 |
----------------------
| 2 |text3 | 1 |
----------------------
| 98 |text4 | 3 |
----------------------
I need to get a Sum of Col3 where Col1 = 98 and Sum of Col3 where Col1 <> 98. The desired result would be 5 and 2.
My SQL query looks like that:
'SELECT sum(case when Col1 = 98 then Col3 else 0 end) as aShort, ' +
'sum(case when Col1 <> 98 then Col3 else 0 end) as aLong '...
And the result that i get is 0 and 7.
What am i doing wrong?
I suppose data type of Col1 is not integer or numeric but of string type such as text or varchar, and seems values contain some whitespaces in them. I strongly recommend to hold a numeric value within a numeric type of column, but in the current case you need to cast as integer in order to get such a result as desired using the query below
SELECT SUM(CASE WHEN CAST(Col1 AS INT) = 98 THEN Col3 ELSE 0 END) AS aShort,
SUM(CASE WHEN CAST(Col1 AS INT) <> 98 THEN Col3 ELSE 0 END) AS aLong
FROM tab
Demo
I need to merge a table with ID and various bit flags like this
-----------------
a1 | x | | x |
-----------------
a1 | | x | |
-----------------
a1 | | | |
-----------------
b2 | x | | |
-----------------
b2 | | | |
-----------------
c3 | x | x | x |
into such form
-----------------
a1 | x | x | x |
-----------------
b2 | x | | |
-----------------
c3 | x | x | x |
The problem is that data are join by kind of option ID each option has an unique ID which is joined with a1, b2. When I try to SELECT it by using DISTINCT I receive results from table number 1. I can make it by subqueries in SELECT but it is really weak solution due to performance reasons.
Do you have any idea how select and combine all these flags into single row?
use aggregation
select col1 ,max(col2),max(col3),max(col4)
form table_name group by col1
For the given result set it is eligible to use MIN and GROUP BY:
SELECT
tbl.Col
, MIN(tbl.Col1) Col1
, MIN(tbl.Col2) Col2
, MIN(tbl.Col3) Col3
FROM #table tbl
GROUP BY tbl.Col
However, if you have empty rows, then use MAX(). Otherwise MIN() returns empty rows:
SELECT
tbl.Col
, MAX(tbl.Col1) Col1
, MAX(tbl.Col2) Col2
, MAX(tbl.Col3) Col3
FROM #table tbl
GROUP BY tbl.Col
For example:
DECLARE #table TABLE
(
Col VARCHAR(50),
Col1 VARCHAR(50),
Col2 VARCHAR(50),
Col3 VARCHAR(50)
)
INSERT INTO #table
(
Col,
Col1,
Col2,
Col3
)
VALUES
( 'a1', -- Col - varchar(50)
'x', -- Col1 - varchar(50)
Null, -- Col2 - varchar(50)
'x' -- Col3 - varchar(50)
)
, ('a1', NULL, 'x', null)
, ('a1', NULL, 'x', null)
, ('b2', 'x', null, null)
, ('b2', null, null, null)
, ('c3', 'x', 'x', 'x')
SELECT
tbl.Col
, MIN(tbl.Col1) Col1
, MIN(tbl.Col2) Col2
, MIN(tbl.Col3) Col3
FROM #table tbl
GROUP BY tbl.Col
OUTPUT:
Col Col1 Col2 Col3
a1 x x x
b2 x NULL NULL
c3 x x x
You want aggregation :
select col1, max(col2), max(col2), max(col3)
from table t
group by col1;
This assuming blank value as null.
The general solution for such a situation is to simply aggregate and either use MIN or MAX on the columns.
SQL Server's data type BIT, however, is quirky. It's a little like a BOOLEAN, but not a real boolean. It is a little like a very limited numeric data type, but it isn't really a numeric type either. And there simply exist no aggregation functions for this data type. In standard SQL you'd have ANY and EVERY for the BOOLEAN type. In PostgreSQL you have BIT_OR and BIT_AND for BIT and BOOL_OR and BOOL_AND for BOOLEAN. SQL Server has nothing.
So convert your columns to a numeric type before using MIN (which would be a bitwise AND) or MAX (which would be a bitwise OR) on it. E.g.
select
id,
max(bit1 + 0) as bit1agg,
max(bit2 + 0) as bit2agg,
max(bit3 + 0) as bit3agg
from mytable
group by id
order by id;
You can also use CAST or CONVERT instead of course.
I have a table tab1 that looks like this:
col1 | col2 | col3
------|------|------
abc | 100 | text
abc | 100 | text
abc | 100 | text
... | ... | ...
I need to update col2 value in each row like this:
update tab1
set col2 = 1,23
when mod(rownum,10) = 1;
update tab1
set col2 = 12,34
when mod(rownum,10) = 2;
update tab1
set col2 = 123,45
when mod(rownum,10) = 3;
and etc. until when mod(rownum,10) = 9.
But obviously this query doesn't work, and the reason is that rownum always returns 1 in this situation, afaik. However, I've got the correct last digits for each row number with select mod(rownum,10) as lastDig from tab1 query. But I don't understand how to use the result of this select for my update when conditions.
Could you please provide an example of a query that will do the job in this situation? Do I need to use a subquery or select in a temporary table? Please explain. I'm a junior frontend guy, but I need to create a demo table this way. I believe, pl/sql is v10, as well as PL/SQL Developer.
Result wanted looks like this:
col1 | col2 | col3
------|-------|------
abc | 1.23 | text
abc | 12.34 | text
abc | 123.45| text
... | ... | ...
You could use CASE expression or DECODE:
update tab1
set col2 = CASE mod(rownum,10) WHEN 1 THEN 1.23
WHEN 2 THEN 12.34
WHEN 3 THEN 123.45
-- ...
ELSE col2
END
-- WHERE ...
UPDATE tab1
SET col2 = DECODE(mod(rownum,10), 1, 1.23, 2, 12.34, 3, 123.45, ..., col2)
-- WHERE ...;
DBFiddle Demo
You have not told us if there is a specific order in which you want to treat rows as 1,2,3 .. If there is indeed an order, then ROWNUM is unreliable and may not work, you would need row_number() with a specific order by column. That can be combined with a MERGE statement.
MERGE INTO tab1 tgt USING (
SELECT
CASE mod( ROW_NUMBER() OVER(
ORDER BY
col1 -- the column which is in order and unique
),10)
WHEN 1 THEN 1.23
WHEN 2 THEN 12.34
WHEN 3 THEN 123.45
--..
--.. 9
ELSE col2
AS col2
FROM
tab1 t
)
src ON ( tgt.rowid = src.rowid ) --use primary key/unique key if there is one instead of rowid
WHEN MATCHED THEN UPDATE SET tgt.col2 = src.col2;
Demo
I have a table with 1 row and 2 columns: col1 and col2,
--------------------------------------------------
| col1 | col2 |
--------------------------------------------------
| 1 | 2 |
--------------------------------------------------
now I want to update the row record:
db2 "update myschema.mytable set col1=3, col2=col1"
I expect the result to be col1=3 and col2=3, but it gives me col1=3,col2=1
how do I update one column base on a newly updated column?
Try This:
DECLARE #A INT
SELECT #A = Col1 FROM Mytable
UPDATE MyTable SET Col1 = 4, Col2 = #A
Is there any way to map the first table to the second table with an SQL query or, if too complicated, a PL/SQL block?
Original
--------------------------------------
| col1 | col2 | col3 | col4 |
--------------------------------------
| key | case 1 | case 2 | case 3 |
| value1 | v1c1 | v1c2 | v1c3 |
| value2 | v2c1 | v2c2 | v2c3 |
--------------------------------------
Target
-----------------------------
| key | case | result |
-----------------------------
| value1 | case 1 | v1c1 |
| value1 | case 2 | v1c2 |
| value1 | case 3 | v1c3 |
| value2 | case 1 | v2c1 |
| value2 | case 2 | v2c2 |
| value2 | case 3 | v2c3 |
-----------------------------
The original table can have a variable number of columns, and 'key' is a hardcoded string and is always in column 1 of the original table. No other row has “key” in column 1, so this row is a unique pivot.
Thank you
If dynamic sql is allowed, then it is possible to have all your requirements fullfilled using one query:
SELECT col1 as "key"
,extractvalue(dbms_xmlgen.getXMLType('select "' || tc.Column_Name ||
'" as v from Original where col1 = ''key''')
,'/ROWSET/ROW/V') "case"
,extractvalue(dbms_xmlgen.getXMLType('select "' || tc.Column_Name ||
'" as v from Original where col1 = ''' ||
replace(col1, '''', '''''') || '''')
,'/ROWSET/ROW/V') "result"
FROM Original
,(SELECT Column_Name
FROM All_Tab_Columns tc
WHERE tc.Owner = 'YOURSCHEMA'
and tc.Table_Name = 'ORIGINAL'
and Column_Name != 'COL1'
ORDER BY tc.COLUMN_ID) tc
WHERE col1 != 'key'
ORDER BY "key"
,"case"
Some more details as requested:
dbms_xmlgen.getXMLType returns an XmlType instance which is basically the result of the supplied query string as XML.
The format is ROWSET for the root node and ROW for each row. Every column will be an element as well.
The 2 selects that I am creating are only returning one value and to makes things easier, I gave them a column alias "V" so that I know which value to pick from the XML.
extractValue is a function that returns the result of an XPath expression from an XmlType.
'/ROWSET/ROW/V' returns the first V node, from the first ROW node that resides under the root node ROWSET.
<ROWSET><ROW><V>Abc</V></ROW></ROWSET>
The original table can have a variable
number of columns
Really?
The straightforward way is to select and union the parts you want.
select col1 as key, 'case1' as case, col2 as result
from test
where col1 <> 'key'
union all
select col1 as key, 'case2' as case, col3 as result
from test
where col1 <> 'key'
union all
select col1 as key, 'case3' as case, col4 as result
from test
where col1 <> 'key'
Straightforward, but not dynamic.
Later . . .
Based on your comment . . . although I don't think it's necessary.
select col1 as key, (select col2 from test where col1='key') as case, col2 as result
from test
where col1 <> 'key'
union all
select col1 as key, (select col3 from test where col1='key') as case, col3 as result
from test
where col1 <> 'key'
union all
select col1 as key, (select col4 from test where col1='key') as case, col4 as result
from test
where col1 <> 'key'
Oracle 11 also supports UNPIVOT, which I haven't used.
I don't know which parts can change, but this should be a start for you. If the column names can change (key, case 1, etc.) you will have to have another query to get the correct column names. If you have questions feel free to ask:
declare
v_query VARCHAR2(5000);
v_case VARCHAR2(255);
v_colcount PLS_INTEGER;
begin
-- Get number of columns
select count(*)
INTO v_colcount
from user_tab_columns
where table_name = 'T1';
-- Build case statement to get correct value for result column
v_case := 'case';
for i in 1 .. v_colcount-1
loop
v_case := v_case||' when rn = '||to_char(i)||' then col'||to_char(i+1);
end loop;
v_case := v_case||' end result';
-- Build final query
v_query := 'select col1 key, ''case ''||rn case, '||v_case||'
from t1
cross join (
select rownum rn
from dual
connect by level <= '||to_char(v_colcount-1)||'
) cj
where col1 <> ''key''
order by key, case';
-- Display query (would probably be replaced with an insert using execute immediate)
dbms_output.put_line(v_query);
end;
This produces the following query (which assumes your original table is called t1):
select col1 key, 'case '||rn case, case when rn = 1 then col2 when rn = 2 then col3 when rn = 3 then col4 end result
from t1
cross join (
select rownum rn
from dual
connect by level <= 3
) cj
where col1 <> 'key'
order by key, case
Try this:
with data as
(select level l from dual connect by level <= 3)
select col1,
'case' || l as "case",
decode(l,1,col2,2,col3,3,col4) as "values"
from myTable, data
order by 1,2;
Cheers