The caret (^) anchors the start, and the dollar sign ($) the end;
mysql>
mysql> SELECT 'abcabcabc' REGEXP 'abc{3}';
+-----------------------------+
| 'abcabcabc' REGEXP 'abc{3}' |
+-----------------------------+
| 0 |
+-----------------------------+
1 row in set (0.00 sec)
mysql>
mysql> SELECT 'abccc' REGEXP 'abc{3}';
+-------------------------+
| 'abccc' REGEXP 'abc{3}' |
+-------------------------+
| 1 |
+-------------------------+
1 row in set (0.00 sec)
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