Eliminate First 14 For Each Symbol From Query - mysql

Question

The following query pulls all rows that do not exist in a relative_strength_index table. But I also need to eliminate the first 14 rows for each symbol based on date asc from the historical_data table. I have tried several attempts to do this but am having real trouble with the 14 days. How could this issue be resolved and added into my current query?
Current Query
select *
from historical_data hd
where not exists (select rsi_symbol, rsi_date from relative_strength_index where hd.symbol = rsi_symbol and hd.histDate = rsi_date);

Answer 1

What you want is the first argument of the limit clause. Which states which row to start from accompanied by order by asc.
select * from historical_data hd where not exists (select rsi_symbol, rsi_date from relative_strength_index where hd.symbol = rsi_symbol and hd.histDate = rsi_date ORDER BY rsi_date ASC LIMIT 14)

Answer 2

use OFFSET along with LIMIT like this this will return maximum of 100,000 rows starting at row 15
select *
from historical_data hd
where not exists (select rsi_symbol, rsi_date from relative_strength_index where hd.symbol = rsi_symbol and hd.histDate = rsi_date)
order by date asc
limit 100000 offset 14;
but because you're using limit and offset, you might want to ORDER BY by some order before specifying limit and offset.
UPDATE you mentioned for each symbol, so try this query, it ranks each symbol based on date asc, then only selects rows where rank >= 15
SELECT *
FROM
(select hd.*,
CASE WHEN #previous_symbol = hd.symbol THEN #rank:=#rank+1
ELSE #rank := 1
END as rank,
#previous_symbol := hd.symbol
from historical_data hd
where not exists (select rsi_symbol, rsi_date from relative_strength_index where hd.symbol = rsi_symbol and hd.histDate = rsi_date)
order by hd.symbol, hd.date asc
)T
WHERE T.rank >= 15

Answer 3

It's not clear (to me) what resultset you want to return, or the conditions that specify whether a row should be returned.
All we have to go on is a confusingly vague description, to exclude "the first 14 rows", or "the first 14 days" for each symbol.
What we don't have is a represetative sample of the data, or an example of what rows should be returned.
Without that, we don't have a way to know if we understand the description of the specification, and we don't have anything to test against or to compare our results to.
So, we are basically just guessing. (Which seems to be the most popular kind of answer provided by the "try this" enthusiatss.)
I can provide some examples of some patterns, which may suit your specification, or may not.
To get the earliest `histdate` for each `symbol`, and add 14 days to that, we can use an inline view. We can then do a semi-join to the `historical_data` data, to exclude rows that have a `histdate` before the date returned from the inline view.
(This is based on an assumption that the datatype of the `histdate` column is DATE.)
SELECT hd.*
FROM ( SELECT d.symbol
, MIN(d.histdate) + INTERVAL 14 DAY AS histdate
FROM historical_data d
GROUP BY d.symbol
) dd
JOIN historical_data hd
ON hd.symbol = dd.symbol
AND hd.histdate > dd.histdate
ORDER
BY hd.symbol
, hd.histdate
But that query doesn't include any reference to the `relative_strength_index` table. The original query includes a NOT EXISTS predicate, with a correlated subquery of the `relative_strength_index` table.
If the goal is get the earliest `rsi_date` for each `rsi_symbol` from that table, and then add 14 days to that value...
SELECT hd.*
FROM ( SELECT rsi.rsi_symbol
, MIN(rsi.rsi_date) + INTERVAL 14 DAY AS rsi_date
FROM relative_strength_index rsi
GROUP BY rsi.rsi_symbol
) rs
JOIN historical_data hd
ON hd.symbol = rs.rsi_symbol
ON hd.histdate > rs.rsi_date
ORDER
BY hd.symbol
, hd.histdate
If the goal is to exclude rows where a matching row in relative_strength_index already exists, I would use an anti-join pattern...
SELECT hd.*
FROM ( SELECT d.symbol
, MIN(d.histdate) + INTERVAL 14 DAY AS histdate
FROM historical_data d
GROUP BY d.symbol
) dd
JOIN historical_data hd
ON hd.symbol = dd.symbol
AND hd.histdate > dd.histdate
LEFT
JOIN relative_strength_index xr
ON xr.rsi_symbol = hd.symbol
AND xr.rsi_date = hd.histdate
WHERE xr.rsi_symbol IS NULL
ORDER
BY hd.symbol
, hd.histdate
These are just example query patterns, which are likely not suited to your exact specification, since they are guesses.
It doesn't make much sense to provide more examples of other patterns, without a more detailed specification.