Related
I have two tables that I need to find the difference between.
What's required is a table of a summary of what fields have changed (ignoring id columns). Also, I don't know which columns have changed.
e.g. Source table [fields that have changed are {name}, {location}; {id} is ignored]
id || name || location || description
1 || aaaa || ddd || abc
2 || bbbb || eee || abc
e.g. Output Table [outputting {name}, {location} as they have changed]
Table_name || Field_changed || field_was || field_now
Source table || name || aaaa || bbbb
Source table || location || ddd || eee
I have tried to use lag(); but that only gives me the columns I selected. Eventually I'd want to see all changes in all columns as I am not sure what columns are changed.
Also please note that the table has about 150 columns - so one of the biggest issues is how to find the ones that changed
As your table can contain multiple changes in a single row and it needs to be calculated in the result as multiple rows, I have created a query to incorporate them separately as follows:
WITH DATAA(ID, NAME, LOCATION, DESCRIPTION)
AS
(SELECT 1, 'aaaa', 'ddd', 'abc' FROM DUAL UNION ALL
SELECT 2, 'bbbb', 'eee', 'abc' FROM DUAL),
-- YOUR QUERY WILL START FROM HERE
CTE AS (SELECT NAME,
LAG(NAME,1) OVER (ORDER BY ID) PREV_NAME,
LOCATION,
LAG(LOCATION,1) OVER (ORDER BY ID) PREV_LOCATION,
DESCRIPTION,
LAG(DESCRIPTION,1) OVER (ORDER BY ID) PREV_DESCRIPTION
FROM DATAA)
--
SELECT
'Source table' AS TABLE_NAME,
FIELD_CHANGED,
FIELD_WAS,
FIELD_NOW
FROM
(
SELECT
'Name' AS FIELD_CHANGED,
PREV_NAME AS FIELD_WAS,
NAME AS FIELD_NOW
FROM
CTE
WHERE
NAME <> PREV_NAME
UNION ALL
SELECT
'location' AS FIELD_CHANGED,
PREV_LOCATION AS FIELD_WAS,
LOCATION AS FIELD_NOW
FROM
CTE
WHERE
LOCATION <> PREV_LOCATION
UNION ALL
SELECT
'description' AS FIELD_CHANGED,
PREV_DESCRIPTION AS FIELD_WAS,
DESCRIPTION AS FIELD_NOW
FROM
CTE
WHERE
DESCRIPTION <> PREV_DESCRIPTION
);
Output:
DEMO
Cheers!!
I have a Table - Product In Oracle, wherein p_spc_cat_id is stored as comma separated values.
p_id p_name p_desc p_spc_cat_id
1 AA AAAA 26,119,27,15,18
2 BB BBBB 0,0,27,56,57,4
3 BB CCCC 26,0,0,15,3,8
4 CC DDDD 26,0,27,7,14,10
5 CC EEEE 26,119,0,48,75
Now I want to search p_name which have p_spc_cat_id in '26,119,7' And this search value are not fixed it will some time '7,27,8'. The search text combination change every time
my query is:
select p_id,p_name from product where p_spc_cat_id in('26,119,7');
when i execute this query that time i can't find any result
I am little late in answering however i hope that i understood the question correctly.
Read further if: you have a table storing records like
1. 10,20,30,40
2. 50,40,20,70
3. 80,60,30,40
And a search string like '10,60', in which cases it should return rows 1 & 3.
Please try below, it worked for my small table & data.
create table Temp_Table_Name (some_id number(6), Ab varchar2(100))
insert into Temp_Table_Name values (1,'112,120')
insert into Temp_Table_Name values (2,'7,8,100,26')
Firstly lets breakdown the logic:
The table contains comma separated data in one of the columns[Column AB].
We have a comma separated string which we need to search individually in that string column. ['26,119,7,18'-X_STRING]
ID column is primary key in the table.
1.) Lets multiple each record in the table x times where x is the count of comma separated values in the search string [X_STRING]. We can use below query to create the cartesian join sub-query table.
Select Rownum Sequencer,'26,119,7,18' X_STRING
from dual
CONNECT BY ROWNUM <= (LENGTH( '26,119,7,18') - LENGTH(REPLACE( '26,119,7,18',',',''))) + 1
Small note: Calculating count of comma separated values =
Length of string - length of string without ',' + 1 [add one for last value]
2.) Create a function PARSING_STRING such that PARSING_STRING(string,position). So If i pass:
PARSING_STRING('26,119,7,18',3) it should return 7.
CREATE OR REPLACE Function PARSING_STRING
(String_Inside IN Varchar2, Position_No IN Number)
Return Varchar2 Is
OurEnd Number; Beginn Number;
Begin
If Position_No < 1 Then
Return Null;
End If;
OurEnd := Instr(String_Inside, ',', 1, Position_No);
If OurEnd = 0 Then
OurEnd := Length(String_Inside) + 1;
End If;
If Position_No = 1 Then
Beginn := 1;
Else
Beginn := Instr(String_Inside, ',', 1, Position_No-1) + 1;
End If;
Return Substr(String_Inside, Beginn, OurEnd-Beginn);
End;
/
3.) Main query, with the join to multiply records.:
select t1.*,PARSING_STRING(X_STRING,Sequencer)
from Temp_Table_Name t1,
(Select Rownum Sequencer,'26,119,7,18' X_STRING from dual
CONNECT BY ROWNUM <= (Select (LENGTH( '26,119,7,18') - LENGTH(REPLACE(
'26,119,7,18',',',''))) + 1 from dual)) t2
Please note that with each multiplied record we are getting 1 particular position value from the comma separated string.
4.) Finalizing the where condition:
Where
/* For when the value is in the middle of the strint [,value,] */
AB like '%,'||PARSING_STRING(X_STRING,Sequencer)||',%'
OR
/* For when the value is in the start of the string [value,]
parsing the first position comma separated value to match*/
PARSING_STRING(AB,1) = PARSING_STRING(X_STRING,Sequencer)
OR
/* For when the value is in the end of the string [,value]
parsing the last position comma separated value to match*/
PARSING_STRING(AB,(LENGTH(AB) - LENGTH(REPLACE(AB,',',''))) + 1) =
PARSING_STRING(X_STRING,Sequencer)
5.) Using distinct in the query to get unique ID's
[Final Query:Combination of all logic stated above: 1 Query to find them all]
select distinct Some_ID
from Temp_Table_Name t1,
(Select Rownum Sequencer,'26,119,7,18' X_STRING from dual
CONNECT BY ROWNUM <= (Select (LENGTH( '26,119,7,18') - LENGTH(REPLACE( '26,119,7,18',',',''))) + 1 from dual)) t2
Where
AB like '%,'||PARSING_STRING(X_STRING,Sequencer)||',%'
OR
PARSING_STRING(AB,1) = PARSING_STRING(X_STRING,Sequencer)
OR
PARSING_STRING(AB,(LENGTH(AB) - LENGTH(REPLACE(AB,',',''))) + 1) = PARSING_STRING(X_STRING,Sequencer)
You can use like to find it:
select p_id,p_name from product where p_spc_cat_id like '%26,119%'
or p_spc_cat_id like '%119,26%' or p_spc_cat_id like '%119,%,26%' or p_spc_cat_id like '%26,%,119%';
Use the Oracle function instr() to achieve what you want. In your case that would be:
SELECT p_name
FROM product
WHERE instr(p_spc_cat_id, '26,119') <> 0;
Oracle Doc for INSTR
If the string which you are searching will always have 3 values (i.e. 2 commas present) then you can use below approach.
where p_spc_cat_id like regexp_substr('your_search_string, '[^,]+', 1, 1)
or p_spc_cat_id like regexp_substr('your_search_string', '[^,]+', 1, 2)
or p_spc_cat_id like regexp_substr('your_search_string', '[^,]+', 1, 3)
If you cant predict how many values will be there in your search string
(rather how many commas) in that case you may need to generate dynamic query.
Unfortunately sql fiddle is not working currently so could not test this code.
SELECT p_id,p_name
FROM product
WHERE p_spc_cat_id
LIKE '%'||'&i_str'||'%'`
where i_str is 26,119,7 or 7,27,8
This solution uses CTE's. "product" builds the main table. "product_split" turns products into rows so each element in p_spc_cat_id is in it's own row. Lastly, product_split is searched for each value in the string '26,119,7' which is turned into rows by the connect by.
with product(p_id, p_name, p_desc, p_spc_cat_id) as (
select 1, 'AA', 'AAAA', '26,119,27,15,18' from dual union all
select 2, 'BB', 'BBBB', '0,0,27,56,57,4' from dual union all
select 3, 'BB', 'CCCC', '26,0,0,15,3,8' from dual union all
select 4, 'CC', 'DDDD', '26,0,27,7,14,10' from dual union all
select 5, 'CC', 'EEEE', '26,119,0,48,75' from dual
),
product_split(p_id, p_name, p_spc_cat_id) as (
select p_id, p_name,
regexp_substr(p_spc_cat_id, '(.*?)(,|$)', 1, level, NULL, 1)
from product
connect by level <= regexp_count(p_spc_cat_id, ',')+1
and prior p_id = p_id
and prior sys_guid() is not null
)
-- select * from product_split;
select distinct p_id, p_name
from product_split
where p_spc_cat_id in(
select regexp_substr('26,119,7', '(.*?)(,|$)', 1, level, NULL, 1) from dual
connect by level <= regexp_count('26,119,7', ',') + 1
)
order by p_id;
P_ID P_
---------- --
1 AA
3 BB
4 CC
5 CC
SQL>
I have two tables both has same value but bot are from different source.
Table 1
------------
ID Title
1 Introduction to Science
2 Introduction to C
3 Let is C
4 C
5 Java
Table 2
------------------------
ID Title
a Intro to Science
b Intro to C
c Let is C
d C
e Java
I want to compare all the title in table 1 with title in table 2 and find the similarity match.
I Have used the built-in function in orcale "UTL_MATCH.edit_distance_similarity (LS_Title, LSO_Title);"
Script:
DECLARE
LS_count NUMBER;
LSO_count NUMBER;
percentage NUMBER;
LS_Title VARCHAR2 (4000);
LSO_Title VARCHAR2 (4000);
LS_CPNT_ID VARCHAR2 (64);
LSO_CPNT_ID VARCHAR2 (64);
BEGIN
SELECT COUNT (*) INTO LS_count FROM tbl_zim_item;
SELECT COUNT (*) INTO LSO_count FROM tbl_zim_lso_item;
DBMS_OUTPUT.put_line ('value of a: ' || LS_count);
DBMS_OUTPUT.put_line ('value of a: ' || LSO_count);
FOR i IN 1 .. LS_count
LOOP
SELECT cpnt_title
INTO LS_Title
FROM tbl_zim_item
WHERE iden = i;
SELECT cpnt_id
INTO LS_CPNT_ID
FROM tbl_zim_item
WHERE iden = i;
FOR j IN 1 .. lso_count
LOOP
SELECT cpnt_title
INTO LSO_Title
FROM tbl_zim_lso_item
WHERE iden = j;
SELECT cpnt_id
INTO LSO_CPNT_ID
FROM tbl_zim_lso_item
WHERE iden = j;
percentage :=
UTL_MATCH.edit_distance_similarity (LS_Title, LSO_Title);
IF percentage > 50
THEN
INSERT INTO title_sim
VALUES (ls_cpnt_id,
ls_title,
lso_cpnt_id,
lso_title,
percentage);
END IF;
END LOOP;
END LOOP;
END;
This is running for more than 15 hours. Kindly provide a better solution.
Note : My table 1 has 20000 records and table 2 has 10000 records.
Unless I'm missing something, you don't need all of the looping and row-by-row lookups since SQL can do cross joins. Therefore my first try would be just:
insert into title_sim
( columns... )
select ls_cpnt_id
, ls_title
, lso_cpnt_id
, lso_title
, percentage
from ( select i.cpnt_id as ls_cpnt_id
, i.cpnt_title as ls_title
, li.cpnt_id as lso_cpnt_id
, li.cpnt_title as lso_title
, case -- Using Boneist's suggestion:
when i.cpnt_title = li.cpnt_title then 100
else utl_match.edit_distance_similarity(i.cpnt_title, li.cpnt_title)
end as percentage
from tbl_zim_item i
cross join tbl_zim_lso_item li )
where percentage > 50;
If there is much repetition in the titles, you might benefit from some scalar subquery caching by wrapping the utl_match.edit_distance_similarity function in a ( select ... from dual ).
If the titles are often exactly the same and assuming in those cases percentage should be 100%, you might avoid calling the function when the titles are an exact match:
begin
select count(*) into ls_count from tbl_zim_item;
select count(*) into lso_count from tbl_zim_lso_item;
dbms_output.put_line('tbl_zim_item contains ' || ls_count || ' rows.');
dbms_output.put_line('tbl_zim_lso_item contains ' || lso_count || ' rows.');
for r in (
select i.cpnt_id as ls_cpnt_id
, i.cpnt_title as ls_title
, li.cpnt_id as lso_cpnt_id
, li.cpnt_title as lso_title
, case
when i.cpnt_title = li.cpnt_title then 100 else 0
end as percentage
from tbl_zim_item i
cross join tbl_zim_lso_item li
)
loop
if r.percentage < 100 then
r.percentage := utl_match.edit_distance_similarity(r.ls_title, r.lso_title);
end if;
if r.percentage > 50 then
insert into title_sim (columns...)
values
( ls_cpnt_id
, ls_title
, lso_cpnt_id
, lso_title
, percentage );
end if;
end loop;
end;
Rather than looping through all the data, I'd merely join the two tables together, eg:
WITH t1 AS (SELECT 1 ID, 'Introduction to Science' title FROM dual UNION ALL
SELECT 2 ID, 'Introduction to C' title FROM dual UNION ALL
SELECT 3 ID, 'Let is C' title FROM dual UNION ALL
SELECT 4 ID, 'C' title FROM dual UNION ALL
SELECT 5 ID, 'Java' title FROM dual UNION ALL
SELECT 6 ID, 'Oracle for Newbies' title FROM dual),
t2 AS (SELECT 'a' ID, 'Intro to Science' title FROM dual UNION ALL
SELECT 'b' ID, 'Intro to C' title FROM dual UNION ALL
SELECT 'c' ID, 'Let is C' title FROM dual UNION ALL
SELECT 'd' ID, 'C' title FROM dual UNION ALL
SELECT 'e' ID, 'Java' title FROM dual UNION ALL
SELECT 'f' ID, 'PL/SQL rocks!' title FROM dual)
SELECT t1.title t1_title,
t2.title t2_title,
UTL_MATCH.edit_distance_similarity(t1.title, t2.title)
FROM t1
INNER JOIN t2 ON UTL_MATCH.edit_distance_similarity(t1.title, t2.title) > 50;
T1_TITLE T2_TITLE UTL_MATCH.EDIT_DISTANCE_SIMILA
----------------------- ---------------- ------------------------------
Introduction to Science Intro to Science 70
Introduction to C Intro to C 59
Let is C Let is C 100
C C 100
Java Java 100
By doing that, you can then reduce the whole thing to a single DML statement, something like:
INSERT INTO title_sim (t1_id,
t1_title,
t2_id,
t2_title,
percentage)
SELECT t1.id t1_id,
t1.title t1_title,
t2.id t2_id,
t2.title t2_title,
UTL_MATCH.edit_distance_similarity(t1.title, t2.title) percentage
FROM t1
INNER JOIN t2 ON UTL_MATCH.edit_distance_similarity(t1.title, t2.title) > 50;
which ought to be a good deal faster than your row-by-row attempt, particularly as you are unnecessarily selecting from each table twice.
As an aside, you know that you can select multiple columns into multiple variables in the same query, right?
So instead of having:
SELECT cpnt_title
INTO LS_Title
FROM tbl_zim_item
WHERE iden = i;
SELECT cpnt_id
INTO LS_CPNT_ID
FROM tbl_zim_item
WHERE iden = i;
you could instead do:
SELECT cpnt_title, cpnt_id
INTO LS_Title, LS_CPNT_ID
FROM tbl_zim_item
WHERE iden = i;
https://www.techonthenet.com/oracle/intersect.php
this will give you data which is similar in both queries
select title from table_1
intersect
select title from table_2
I have data like this in a table
NAME PRICE
A 2
B 3
C 5
D 9
E 5
I want to display all the values in one row; for instance:
A,2|B,3|C,5|D,9|E,5|
How would I go about making a query that will give me a string like this in Oracle? I don't need it to be programmed into something; I just want a way to get that line to appear in the results so I can copy it over and paste it in a word document.
My Oracle version is 10.2.0.5.
-- Oracle 10g --
SELECT deptno, WM_CONCAT(ename) AS employees
FROM scott.emp
GROUP BY deptno;
Output:
10 CLARK,MILLER,KING
20 SMITH,FORD,ADAMS,SCOTT,JONES
30 ALLEN,JAMES,TURNER,BLAKE,MARTIN,WARD
I know this is a little late but try this:
SELECT LISTAGG(CONCAT(CONCAT(NAME,','),PRICE),'|') WITHIN GROUP (ORDER BY NAME) AS CONCATDATA
FROM your_table
Usually when I need something like that quickly and I want to stay on SQL without using PL/SQL, I use something similar to the hack below:
select sys_connect_by_path(col, ', ') as concat
from
(
select 'E' as col, 1 as seq from dual
union
select 'F', 2 from dual
union
select 'G', 3 from dual
)
where seq = 3
start with seq = 1
connect by prior seq+1 = seq
It's a hierarchical query which uses the "sys_connect_by_path" special function, which is designed to get the "path" from a parent to a child.
What we are doing is simulating that the record with seq=1 is the parent of the record with seq=2 and so fourth, and then getting the full path of the last child (in this case, record with seq = 3), which will effectively be a concatenation of all the "col" columns
Adapted to your case:
select sys_connect_by_path(to_clob(col), '|') as concat
from
(
select name || ',' || price as col, rownum as seq, max(rownum) over (partition by 1) as max_seq
from
(
/* Simulating your table */
select 'A' as name, 2 as price from dual
union
select 'B' as name, 3 as price from dual
union
select 'C' as name, 5 as price from dual
union
select 'D' as name, 9 as price from dual
union
select 'E' as name, 5 as price from dual
)
)
where seq = max_seq
start with seq = 1
connect by prior seq+1 = seq
Result is: |A,2|B,3|C,5|D,9|E,5
As you're in Oracle 10g you can't use the excellent listagg(). However, there are numerous other string aggregation techniques.
There's no particular need for all the complicated stuff. Assuming the following table
create table a ( NAME varchar2(1), PRICE number);
insert all
into a values ('A', 2)
into a values ('B', 3)
into a values ('C', 5)
into a values ('D', 9)
into a values ('E', 5)
select * from dual
The unsupported function wm_concat should be sufficient:
select replace(replace(wm_concat (name || '#' || price), ',', '|'), '#', ',')
from a;
REPLACE(REPLACE(WM_CONCAT(NAME||'#'||PRICE),',','|'),'#',',')
--------------------------------------------------------------------------------
A,2|B,3|C,5|D,9|E,5
But, you could also alter Tom Kyte's stragg, also in the above link, to do it without the replace functions.
Here is another approach, using model clause:
-- sample of data from your question
with t1(NAME1, PRICE) as(
select 'A', 2 from dual union all
select 'B', 3 from dual union all
select 'C', 5 from dual union all
select 'D', 9 from dual union all
select 'E', 5 from dual
) -- the query
select Res
from (select name1
, price
, rn
, res
from t1
model
dimension by (row_number() over(order by name1) rn)
measures (name1, price, cast(null as varchar2(101)) as res)
(res[rn] order by rn desc = name1[cv()] || ',' || price[cv()] || '|' || res[cv() + 1])
)
where rn = 1
Result:
RES
----------------------
A,2|B,3|C,5|D,9|E,5|
SQLFiddle Example
Something like the following, which is grossly inefficient and untested.
create function foo returning varchar2 as
(
declare bar varchar2(8000) --arbitrary number
CURSOR cur IS
SELECT name,price
from my_table
LOOP
FETCH cur INTO r;
EXIT WHEN cur%NOTFOUND;
bar:= r.name|| ',' ||r.price || '|'
END LOOP;
dbms_output.put_line(bar);
return bar
)
Managed to get till here using xmlagg: using oracle 11G from sql fiddle.
Data Table:
COL1 COL2 COL3
1 0 0
1 1 1
2 0 0
3 0 0
3 1 0
SELECT
RTRIM(REPLACE(REPLACE(
XMLAgg(XMLElement("x", col1,',', col2, col3)
ORDER BY col1), '<x>'), '</x>', '|')) AS COLS
FROM ab
;
Results:
COLS
1,00| 3,00| 2,00| 1,11| 3,10|
* SQLFIDDLE DEMO
Reference to read on XMLAGG
I have a PostgreSQL function (or table) which gives me the following output:
Sl.no username Designation salary etc..
1 A XYZ 10000 ...
2 B RTS 50000 ...
3 C QWE 20000 ...
4 D HGD 34343 ...
Now I want the Output as below:
Sl.no 1 2 3 4 ...
Username A B C D ...
Designation XYZ RTS QWE HGD ...
Salary 10000 50000 20000 34343 ...
How to do this?
SELECT
unnest(array['Sl.no', 'username', 'Designation','salary']) AS "Columns",
unnest(array[Sl.no, username, value3Count,salary]) AS "Values"
FROM view_name
ORDER BY "Columns"
Reference : convertingColumnsToRows
Basing my answer on a table of the form:
CREATE TABLE tbl (
sl_no int
, username text
, designation text
, salary int
);
Each row results in a new column to return. With a dynamic return type like this, it's hardly possible to make this completely dynamic with a single call to the database. Demonstrating solutions with two steps:
Generate query
Execute generated query
Generally, this is limited by the maximum number of columns a table can hold. So not an option for tables with more than 1600 rows (or fewer). Details:
What is the maximum number of columns in a PostgreSQL select query
Postgres 9.4+
Dynamic solution with crosstab()
Use the first one you can. Beats the rest.
SELECT 'SELECT *
FROM crosstab(
$ct$SELECT u.attnum, t.rn, u.val
FROM (SELECT row_number() OVER () AS rn, * FROM '
|| attrelid::regclass || ') t
, unnest(ARRAY[' || string_agg(quote_ident(attname)
|| '::text', ',') || '])
WITH ORDINALITY u(val, attnum)
ORDER BY 1, 2$ct$
) t (attnum bigint, '
|| (SELECT string_agg('r'|| rn ||' text', ', ')
FROM (SELECT row_number() OVER () AS rn FROM tbl) t)
|| ')' AS sql
FROM pg_attribute
WHERE attrelid = 'tbl'::regclass
AND attnum > 0
AND NOT attisdropped
GROUP BY attrelid;
Operating with attnum instead of actual column names. Simpler and faster. Join the result to pg_attribute once more or integrate column names like in the pg 9.3 example.
Generates a query of the form:
SELECT *
FROM crosstab(
$ct$
SELECT u.attnum, t.rn, u.val
FROM (SELECT row_number() OVER () AS rn, * FROM tbl) t
, unnest(ARRAY[sl_no::text,username::text,designation::text,salary::text]) WITH ORDINALITY u(val, attnum)
ORDER BY 1, 2$ct$
) t (attnum bigint, r1 text, r2 text, r3 text, r4 text);
This uses a whole range of advanced features. Just too much to explain.
Simple solution with unnest()
One unnest() can now take multiple arrays to unnest in parallel.
SELECT 'SELECT * FROM unnest(
''{sl_no, username, designation, salary}''::text[]
, ' || string_agg(quote_literal(ARRAY[sl_no::text, username::text, designation::text, salary::text])
|| '::text[]', E'\n, ')
|| E') \n AS t(col,' || string_agg('row' || sl_no, ',') || ')' AS sql
FROM tbl;
Result:
SELECT * FROM unnest(
'{sl_no, username, designation, salary}'::text[]
,'{10,Joe,Music,1234}'::text[]
,'{11,Bob,Movie,2345}'::text[]
,'{12,Dave,Theatre,2356}'::text[])
AS t(col,row1,row2,row3,row4);
db<>fiddle here
Old sqlfiddle
Postgres 9.3 or older
Dynamic solution with crosstab()
Completely dynamic, works for any table. Provide the table name in two places:
SELECT 'SELECT *
FROM crosstab(
''SELECT unnest(''' || quote_literal(array_agg(attname))
|| '''::text[]) AS col
, row_number() OVER ()
, unnest(ARRAY[' || string_agg(quote_ident(attname)
|| '::text', ',') || ']) AS val
FROM ' || attrelid::regclass || '
ORDER BY generate_series(1,' || count(*) || '), 2''
) t (col text, '
|| (SELECT string_agg('r'|| rn ||' text', ',')
FROM (SELECT row_number() OVER () AS rn FROM tbl) t)
|| ')' AS sql
FROM pg_attribute
WHERE attrelid = 'tbl'::regclass
AND attnum > 0
AND NOT attisdropped
GROUP BY attrelid;
Could be wrapped into a function with a single parameter ...
Generates a query of the form:
SELECT *
FROM crosstab(
'SELECT unnest(''{sl_no,username,designation,salary}''::text[]) AS col
, row_number() OVER ()
, unnest(ARRAY[sl_no::text,username::text,designation::text,salary::text]) AS val
FROM tbl
ORDER BY generate_series(1,4), 2'
) t (col text, r1 text,r2 text,r3 text,r4 text);
Produces the desired result:
col r1 r2 r3 r4
-----------------------------------
sl_no 1 2 3 4
username A B C D
designation XYZ RTS QWE HGD
salary 10000 50000 20000 34343
Simple solution with unnest()
SELECT 'SELECT unnest(''{sl_no, username, designation, salary}''::text[] AS col)
, ' || string_agg('unnest('
|| quote_literal(ARRAY[sl_no::text, username::text, designation::text, salary::text])
|| '::text[]) AS row' || sl_no, E'\n , ') AS sql
FROM tbl;
Slow for tables with more than a couple of columns.
Generates a query of the form:
SELECT unnest('{sl_no, username, designation, salary}'::text[]) AS col
, unnest('{10,Joe,Music,1234}'::text[]) AS row1
, unnest('{11,Bob,Movie,2345}'::text[]) AS row2
, unnest('{12,Dave,Theatre,2356}'::text[]) AS row3
, unnest('{4,D,HGD,34343}'::text[]) AS row4
Same result.
If (like me) you were needing this information from a bash script, note there is a simple command-line switch for psql to tell it to output table columns as rows:
psql mydbname -x -A -F= -c "SELECT * FROM foo WHERE id=123"
The -x option is the key to getting psql to output columns as rows.
I have a simpler approach than Erwin pointed above, that worked for me with Postgres (and I think that it should work with all major relational databases whose support SQL standard)
You can use simply UNION instead of crosstab:
SELECT text 'a' AS "text" UNION SELECT 'b';
text
------
a
b
(2 rows)
Of course that depends on the case in which you are going to apply this. Considering that you know beforehand what fields you need, you can take this approach even for querying different tables. I.e.:
SELECT 'My first metric' as name, count(*) as total from first_table UNION
SELECT 'My second metric' as name, count(*) as total from second_table
name | Total
------------------|--------
My first metric | 10
My second metric | 20
(2 rows)
It's a more maintainable approach, IMHO. Look at this page for more information: https://www.postgresql.org/docs/current/typeconv-union-case.html
There is no proper way to do this in plain SQL or PL/pgSQL.
It will be way better to do this in the application, that gets the data from the DB.