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POMysql select ordinal
 

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    <p>Having a table named books which has the following structure:</p> <pre><code>╔════════════╦═══════════╦════════╗ ║ LibraryId ║ BookId ║ Price ║ ╠════════════╬═══════════╬════════╣ ║ 123 ║ 9001 ║ 10.99 ║ ║ 123 ║ 9005 ║ 12.99 ║ ║ 123 ║ 9006 ║ 7.99 ║ ║ 124 ║ 8012 ║ 6.49 ║ ║ 124 ║ 9001 ║ 3.19 ║ ║ 124 ║ 9076 ║ 7.39 ║ ╚════════════╩═══════════╩════════╝ </code></pre> <p>How could I do a select that would return the full table, but additionally a field named Ordinal, that "counts" the number of books per library. The result should look something like:</p> <pre><code>╔════════════╦═══════════╦════════╦════════╗ ║ LibraryId ║ BookId ║ Price ║Ordinal ║ ╠════════════╬═══════════╬════════╬════════╣ ║ 123 ║ 9001 ║ 10.99 ║ 1 ║ ║ 123 ║ 9005 ║ 12.99 ║ 2 ║ ║ 123 ║ 9006 ║ 7.99 ║ 3 ║ ║ 124 ║ 8012 ║ 6.49 ║ 1 ║ ║ 124 ║ 9001 ║ 3.19 ║ 2 ║ ║ 124 ║ 9076 ║ 7.39 ║ 3 ║ ╚════════════╩═══════════╩════════╝════════╝ </code></pre> <p>I have tried something like:</p> <pre><code>SET @var_record = 1; SELECT *, (@var_record := @var_record + 1) AS Ordinal FROM books; </code></pre> <p>But this will continue counting irrespective of the libraryId. I need something that will reset the ordinal every time the libraryId changes. I'd prefer a single query instead of procedures.</p> <hr> <p>Test data sql scripts:</p> <pre><code>create temporary table books(libraryId int, bookId int, price double(4,2)); insert into books (libraryId, bookId, price) values (123, 9001, 10.99),(123, 9005, 10.99),(123, 9006, 10.99),(124, 8001, 10.99),(124, 9001, 10.99),(124, 9076, 10.99); </code></pre>
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