Re: Find one record
От | Josh Berkus |
---|---|
Тема | Re: Find one record |
Дата | |
Msg-id | 200309181053.57709.josh@agliodbs.com обсуждение исходный текст |
Ответ на | Find one record (Joseph Bove <jbove@vetstar.com>) |
Список | pgsql-performance |
Joseph, > I hope this to be a simple question. I have need to simply read the first > row in a given table. Right now, I have some legacy code that selects all > rows in a table just to see if the first row has a certain value. Your problem is conceptual: in SQL, there is no "first" row. If you want to just pick a single row at random, do SELECT * FROM table LIMIT 1; Or if you have a primary key id, you could for example return the row with the lowest id: SELECT * FROM table ORDER BY id LIMIT 1; > The code is seeking to see if an update has been run or not. A hypothetical > scenario would be: has an update been run to populate data into a new > column in a table. Neither the data nor any of the rows are consistently > known. So the test selects all rows, tests the first row and then ends if > the column has a value. I'd write an ON UPDATE trigger, personally, to fire and write data somewhere else whenever the table is updated. Much more reliable .... -- Josh Berkus Aglio Database Solutions San Francisco
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