Completely Unique Rows and Columns in SQL - sql

Question

I want to randomly pick 4 rows which are distinct and do not have any entry that matches with any of the 4 chosen columns.
Here is what I coded:
SELECT DISTINCT en,dialect,fr FROM words ORDER BY RANDOM() LIMIT 4
Here is some data:
**en** **dialect** **fr**
number SFA numero
number TRI numero
hotel CAI hotel
hotel SFA hotel
I want:
**en** **dialect** **fr**
number SFA numero
hotel CAI hotel
Some retrieved rows would have something similar with each other, like having the same en or the same fr, I would like to retrieved rows that do not share anything similar with each other, how do I do that?

Answer 1

I think I’d do this in the front end code rather the dB, here’s a pseudo code (don’t know what your node looks like):
var seenEn = “en not in (''“;
var seenFr = “fr not in (''“;
var rows =[];
while(rows.length < 4)
{
var newrow = sqlquery(“SELECT *
FROM table WHERE “ + seenEn + “) and ”
+ seenFr + “) ORDER BY random() LIMIT 1”);
if(!newrow)
break;
rows.push(newrow);
seenEn += “,‘“+ newrow.en + “‘“;
seenFr += “,‘“+ newrow.fr + “‘“;
}
The loop runs as many times as needed to retrieve 4 rows (or maybe make it a for loop that runs 4 times) unless the query returns null. Each time the query returns the values are added to a list of values we don’t want the query to return again. That list had to start out with some values (null) that are never in the data, to prevent a syntax error when concatenation a comma-value string onto the seenXX variable. Those syntax errors can be avoided in other ways like having a Boolean of “if it’s the first value don’t put the comma” but I chose to put dummy ineffective values into the sql to make the JS simpler. Same goes for the
As noted, it looks like JS to ease your understanding but this should be treated as pseudo code outlining a general algorithm - it’s never been compiled/run/tested and may have syntax errors or not at all work as JS if pasted into your file; take the idea and work it into your solution
Please note this was posted from an iphone and it may have done something stupid with all the apostrophes and quotes (turned them into the curly kind preferred by writers rather than the straight kind used by programmers)

Answer 2

You can use Rank or find first row for each group to achieve your result,
Check below , I hope this code will help you
SELECT 'number' AS Col1, 'SFA' AS Col2, 'numero' AS Col3 INTO #tbl
UNION ALL
SELECT 'number','TRI','numero'
UNION ALL
SELECT 'hotel','CAI' ,'hotel'
UNION ALL
SELECT 'hotel','SFA','hotel'
UNION ALL
SELECT 'Location','LocationA' ,'Location data'
UNION ALL
SELECT 'Location','LocationB','Location data'
;
WITH summary AS (
SELECT Col1,Col2,Col3,
ROW_NUMBER() OVER(PARTITION BY p.Col1 ORDER BY p.Col2 DESC) AS rk
FROM #tbl p)
SELECT s.Col1,s.Col2,s.Col3
FROM summary s
WHERE s.rk = 1
DROP TABLE #tbl