MySQL Developing And Programming Blog

Working with MySQL SQL 46 Most dialects of GROUP BY require that the fields used in the clause be part of the SELECT itself. MySQL allows columns to be in the SELECT that aren t part of the GROUP BY. Limit In all the queries so far, all of the rows in the result are returned. There are times when you might want only a single row or a small set when there are many possible result rows. In such cases, you can limit the row count by using the LIMIT clause. For example: mysql> SELECT * FROM acc LIMIT 3; +———+———–+———-+—————-+ | acc_id | username | password | ts | +———+———–+———-+—————-+ | 1034033 | jsmith | smithy | 20021014165845 | | 1034034 | jime | NULL | 20021014165845 | | 1034067 | jthompson | james2 | 20021014165845 | +———+———–+———-+—————-+ 3 rows in set (0.00 sec) In this query example, the first three rows of the result are returned. We can execute the query again and pull another three rows, but instead of starting at the first row in the result, we use an offset value to get the next three rows. For example: mysql> SELECT * FROM acc LIMIT 3,3; +———+———–+———-+—————-+ | acc_id | username | password | ts | +———+———–+———-+—————-+ | 1034089 | sstanford | stanford | 20021014165845 | | 1034123 | blewis | lewis | 20021014165845 | | 1034154 | ysheets | sheets | 20021014165845 | +———+———–+———-+—————-+ 3 rows in set (0.00 sec) In this query, the code offsets to the fourth row and displays three of the results. If there aren t enough rows remaining in the result set, the system returns as many as it can. Dump to File Not all applications are able to use the output from a SQL query, but they are able to handle input in the form of a text file. The SELECT command in MySQL includes a clause called INTO [OUTFILE | DUMPFILE] that allows the result of a query to be placed in a file. As listed, there are two options for the INTO clause: OUTFILE and DUMPFILE. The OUTFILE option is used to dump all rows returned in a query. For example:
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