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Let's say you have the following table (the column of interest here is cid):
+-----+-------+-------+-------+---------------------+--------------+ | cid | pid | rid | clink | time | snippet | +-----+-------+-------+-------+---------------------+--------------+ | 155 | 11222 | 1499 | 1137 | 2012-08-22 03:05:06 | hi | | 138 | 11222 | 241 | 1136 | 2012-08-21 05:25:00 | again | | 138 | 11222 | 241 | 1135 | 2012-08-21 05:16:40 | hi | | 155 | 11222 | 1499 | 1134 | 2012-08-21 05:11:00 | hi cute | | 140 | 11222 | 11223 | 1133 | 2012-08-21 05:05:18 | hi | | 154 | 11222 | 565 | 1132 | 2012-08-21 05:04:47 | 7 | | 153 | 11222 | 272 | 1131 | 2012-08-21 05:04:41 | 6 | | 146 | 11222 | 362 | 1130 | 2012-08-21 05:04:33 | 5 | | 152 | 11222 | 364 | 1129 | 2012-08-21 05:04:27 | 4 | | 151 | 11222 | 390 | 1128 | 2012-08-21 05:04:22 | 3 | | 150 | 11222 | 333 | 1127 | 2012-08-21 05:04:16 | 2 | | 148 | 11222 | 268 | 1126 | 2012-08-21 05:04:10 | 1 | | 140 | 11222 | 11223 | 1125 | 2012-08-21 04:59:57 | hi sir | | 147 | 11222 | 283 | 1123 | 2012-08-21 03:29:55 | yo | | 140 | 11222 | 11223 | 1121 | 2012-08-21 02:12:13 | hello! | | 139 | 11222 | 249 | 1120 | 2012-08-21 02:11:53 | hi :) | | 140 | 11222 | 11223 | 1119 | 2012-08-21 02:11:26 | hi :) | | 140 | 11222 | 11223 | 1118 | 2012-08-21 02:11:08 | hi too | | 139 | 11222 | 249 | 1117 | 2012-08-21 02:11:00 | :P | | 139 | 11222 | 249 | 1116 | 2012-08-21 02:10:57 | hi | | 139 | 11222 | 249 | 1115 | 2012-08-21 02:10:51 | helo | | 139 | 11222 | 249 | 1114 | 2012-08-21 02:06:19 | hi | | 139 | 11222 | 249 | 1113 | 2012-08-21 02:05:45 | hi baby | | 139 | 11222 | 249 | 1112 | 2012-08-21 02:05:00 | hi | | 139 | 11222 | 249 | 1111 | 2012-08-21 02:04:41 | hi | | 140 | 11222 | 11223 | 1110 | 2012-08-21 02:04:26 | hi | | 140 | 11222 | 11223 | 1108 | 2012-08-21 01:47:40 | hey :) | | 139 | 11222 | 249 | 1107 | 2012-08-21 01:44:43 | hi | | 138 | 11222 | 241 | 1106 | 2012-08-21 01:44:11 | hi | | 138 | 11222 | 241 | 1105 | 2012-08-21 01:09:20 | conv 1 msg 1 | +-----+-------+-------+-------+---------------------+--------------+ How to extract only the first occurrence of each cid? The resulting table would be:
+-----+-------+-------+-------+---------------------+--------------+ | cid | pid | rid | clink | time | snippet | +-----+-------+-------+-------+---------------------+--------------+ | 155 | 11222 | 1499 | 1137 | 2012-08-22 03:05:06 | hi | | 138 | 11222 | 241 | 1136 | 2012-08-21 05:25:00 | again | | 140 | 11222 | 11223 | 1133 | 2012-08-21 05:05:18 | hi | | 154 | 11222 | 565 | 1132 | 2012-08-21 05:04:47 | 7 | | 153 | 11222 | 272 | 1131 | 2012-08-21 05:04:41 | 6 | | 146 | 11222 | 362 | 1130 | 2012-08-21 05:04:33 | 5 | | 152 | 11222 | 364 | 1129 | 2012-08-21 05:04:27 | 4 | | 151 | 11222 | 390 | 1128 | 2012-08-21 05:04:22 | 3 | | 150 | 11222 | 333 | 1127 | 2012-08-21 05:04:16 | 2 | | 148 | 11222 | 268 | 1126 | 2012-08-21 05:04:10 | 1 | | 147 | 11222 | 283 | 1123 | 2012-08-21 03:29:55 | yo | | 140 | 11222 | 11223 | 1121 | 2012-08-21 02:12:13 | hello! | | 139 | 11222 | 249 | 1120 | 2012-08-21 02:11:53 | hi :) | +-----+-------+-------+-------+---------------------+--------------+ 
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Select * from any table will fetch and display all the column in that table, while Select 1 from any table will display one row with 1 without any column name.
You can use the DISTINCT command along with the SELECT statement to find out unique records available in a table. mysql> SELECT DISTINCT last_name, first_name -> FROM person_tbl -> ORDER BY last_name; An alternative to the DISTINCT command is to add a GROUP BY clause that names the columns you are selecting.
mysql has a "cheat" for this:
select * from mytable group by cid; That's all you need, because in mysql it allows you to not aggregate the non-grouped-by columns (other databases would throw a syntax error), in which case it outputs only the first occurrence of each group-by value(s). Note though that this won't guarantee the way in which the "first" occurrence is determined (it will be just how the rows are read in)
If you want a particular first occurrence, sort first, then apply the group-by cheat:
select * from ( -- order by the "time" column descending to get the "most recent" row select * from mytable order by time desc ) x group by cid Try this one,
SELECT * FROM tableName a INNER JOIN ( SELECT cid, MIN(`time`) AS MinTime FROM tableName GROUP BY cid ) b ON a.CID = B.cid AND a.time = b.MinTime If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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