问题描述:

In one of my tables, some customers have multiple lines - this could be due to re-visits from technicians etc. What I want to do is for each customer ID, analyse whether a re-vist has taken place and place a marker against their name.

I have tried to combine an if/in statement that analyses the max/min visit dates for each customert ID. So if the max>min its classed as a "re-visit", however, i keep getting a syntax error.

Can someone help?

网友答案:

This is a job for two SQL queries:

1st query:

SELECT customerID, count(customerID) as visitCount
FROM tableOfInterest
GROUP BY customerID

2nd query uses first query:

UPDATE customerManifest INNER JOIN queryAbove ON queryAbove.customerID = customerManifest.customerID
SET customerManifest.multipleVisitIndicatorField to queryAbove.visitCount
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