+Expected Results PAT ID Average Days Kept 1160 53.00 1210 49.00 1185 30.00 1165 28.67 1209 28.33 1207 5.50 1172 4.50 1183 4.33 1171 3.67 1181 3.67 Actual Results PAT ID AVERAGE DATE KEPT 1160 7.0000 1161 3.3333 1165 5.6667 1171 3.6667 1172 4.5000 1181 3.6667 1183 4.3333 1185 6.6667 1207 5.5000 1209 5.3333
SQL
SQL stands for Structured Query Language, is a form of communication that uses queries structured in a specific format to store, manage & retrieve data from a relational database.
Queries
A query is a type of computer programming language that is used to retrieve data from a database. Databases are useful in a variety of ways. They enable the retrieval of records or parts of records, as well as the performance of various calculations prior to displaying the results. A search query is one type of query that many people perform several times per day. A search query is executed every time you use a search engine to find something. When you press the Enter key, the keywords are sent to the search engine, where they are processed by an algorithm that retrieves related results from the search index. Your query's results are displayed on a search engine results page, or SER.
Problem 104
Write a query to display the patron ID and the average number of days that patron keeps books during a checkout. Limit the results to only patrons who have at least three checkouts. Sort the results in descending order by the average days the book is kept, and then in ascending order by patron ID (Figure P7.104).
SELECT P.PAT_ID, AVG(DATEDIFF(C.CHECK_IN_DATE,C.CHECK_OUT_DATE) ) AS "AVERAGE DATE KEPT" FROM PATRON P JOIN CHECKOUT C ON P.PAT_ID=C.PAT_ID GROUP BY P.PAT_ID HAVING COUNT(C.CHECK_OUT_DATE) >= 3 Order by "AVERAGE DAYS KEPT" DESC,P.PAT_ID ASC;
With the query below I am getting the wrong headers were returned, some expected rows were missing and some unexpected rows were returned.
How can i correct this query to ge the expected results? Thanks
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