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To query multiple tables you will have to join them on a key - what we saw as a UNIQUE KEY in the structure
SELECT a.column_names, b.column_names FROM a LEFT JOIN b ON (a.key=b.key);
SELECT branches.branchname, items.barcode, COUNT(issues.issuedate) as totalissues FROM branches LEFT JOIN issues ON (issues.branchcode = branches.branchcode) LEFT JOIN items ON (issues.itemnumber = items.itemnumber) GROUP BY items.barcode;
SELECT borrowers.cardnumber,borrowers.surname,borrowers.firstname,FORMAT(SUM(accountlines.amountoutstanding),2) as due FROM borrowers LEFT JOIN accountlines on (borrowers.borrowernumber=accountlines.borrowernumber) WHERE accountlines.amountoutstanding > 0 GROUP BY borrowers.cardnumber ORDER BY borrowers.surname asc
SELECT borrowers.cardnumber,borrowers.surname,borrowers.firstname,items.barcode,issues.date_due FROM borrowers LEFT JOIN issues on (issues.borrowernumber = borrowers.borrowernumber) LEFT JOIN items on (items.itemnumber = issues.itemnumber) WHERE issues.date_due < DATE_SUB(now(), INTERVAL 12 DAY) AND issues.returndate is NULL ORDER BY borrowers.surname asc
Total number of items circulated from a branch other than the owning branch
SELECT count(*) as total from statistics LEFT JOIN items on (statistics.itemnumber = items.itemnumber) where statistics.branch != items.homebranch AND statistics.datetime between '2008-01-01' and '2008-12-31'
How many new children's (shelving locations) books (Item types) did Library X add to the shared catalog in November 2008?
SELECT count(i.biblionumber) as added, i.itype, i.homebranch, i.location from items i WHERE YEAR(i.dateaccessioned) = 2008 AND MONTH(i.dateaccessioned) = 10 AND i.itype = 'BOOK' AND i.location = 'CHILDRENS' GROUP BY i.homebranch ORDER BY i.location asc