Is there a function for MySQL that will count the number of times a string occurs in another string or column? Basically I want:
SELECT
SUB_COUNT('my word', `my_column`) AS `match_count`
FROM `table`
Thanks!
EDIT:
I need to know how many times t开发者_运维问答he string appears in a column for each row in a SELECT
.
An obvious but unscalable way is like this
(LENGTH(`my_column`) - LENGTH(REPLACE(`my_column`, 'my word', '')))/LENGTH('my word')
Have you investigated Full Text search in MySQL?
I just needed to do something similar, but took a different approach. I copied the relevant string into a temp table where I can add columns to track an index through each occurrence on each row.
In my example, I'm looking for substrings " - " (space-dash-space) in product descriptions, with the intent of eventually chopping those apart to show as bullet points, and I'm analyzing the data like this to see how many "bullets" products typically have.
I suspect this is more efficient than repeatedly re-writing string values, but I haven't actually benchmarked.
SELECT
ccp.ProductID, p.ProductDescription, descrlen=LEN(p.ProductDescription),
bulletcnt=0, indx=0, lastmatchat=0
INTO #DescrBullets
FROM Private.CompositeCatalogProduct AS ccp WITH(NOLOCK)
INNER JOIN Products.Product AS p WITH(NOLOCK) ON p.ProductId = ccp.ProductID
WHERE ccp.CompositeCatalogID=53
DECLARE @rows INT = 1
WHILE @rows>0
BEGIN
-- find the next occurrence on each row that's still in play
UPDATE #DescrBullets
SET lastmatchat = PATINDEX('% - %',RIGHT(ProductDescription,descrlen-indx))
WHERE indx<descrlen
-- anywhere that a match was found, increment my counter, and move my
-- index "cursor" past it
UPDATE #DescrBullets
SET bulletcnt = bulletcnt + 1,
indx = indx + lastmatchat + 2
WHERE lastmatchat>0
SET @rows = @@ROWCOUNT
-- for all the ones that didn't have a match, advance indx past the end
-- so we don't need to reprocess on next iterations
UPDATE #DescrBullets
SET indx=descrlen
WHERE lastmatchat=0
RAISERROR('processing, %d products still have bullets', 0, 1, @rows) WITH NOWAIT
END
SELECT db.bulletcnt, occurs=COUNT(*)
FROM #DescrBullets AS db
GROUP BY db.bulletcnt
ORDER BY 1
I think you may be able to use the following example. I was trying to count the number of times a particular carton type was used when shipping.
SELECT carton_type, COUNT(carton_type) AS match_count
FROM carton_hdr
WHERE whse ='wh1'
GROUP BY "carton_type"
Your scenario:
SELECT my_column COUNT(my_column)
FROM my_table
WHERE my_column = 'my_word'
GROUP BY my_column
If you take out the "where" function, it will count the number of times each distinct entry appears in "my_column".
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