Indexed Lookups from TIMESTAMP Columns •Descending indexes are supported for ordinary (nongenerated) and generated columns (both  VIRTUAL and  STORED ). • DISTINCT  can use any index containing matching columns, including descending key parts. •Indexes that have descending key parts are not used for  MIN() / MAX()  optimization of queries that invoke aggregate functions but do not have a  GROUP BY  clause. •Descending indexes are supported for  BTREE  but not  HASH  indexes. Descending indexes are not supported for  FULLTEXT  or  SPATIAL  indexes. 1730 mysql>  CREATE TABLE tstable (ts TIMESTAMP); mysql>  SET time_zone = ’UTC’; -- insert UTC values mysql>  INSERT INTO tstable VALUES mysql>  EXPLAIN FORMAT=TREE SELECT * FROM t1 ORDER BY a ASC\G *************************** 1. row *************************** EXPLAIN: -> Index scan on t1 using a_desc_b_asc (reverse) (cost=0.35 rows=1) mysql>  CREATE TABLE t1 ( ->  a INT, ->  b INT, ->  INDEX a_desc_b_asc (a DESC, b ASC) ->  ); mysql>  EXPLAIN SELECT * FROM t1 ORDER BY a ASC\G *************************** 1. row *************************** id: 1 select_type: SIMPLE table: t1 partitions: NULL type: index possible_keys: NULL key: a_desc_b_asc key_len: 10 ref: NULL rows: 1 filtered: 100.00 Extra: Backward index scan; Using index Explicitly specified  ASC  and  DESC  designators for  HASH ,  FULLTEXT , and  SPATIAL  indexes results in an error. You can see in the  Extra  column of the output of  EXPLAIN  that the optimizer is able to use a descending index, as shown here: In  EXPLAIN FORMAT=TREE  output, use of a descending index is indicated by the addition of  (reverse) following the name of the index, like this: See also EXPLAIN Extra Information. Temporal values are stored in  TIMESTAMP  columns as UTC values, and values inserted into and retrieved from  TIMESTAMP  columns are converted between the session time zone and UTC. (This is the same type of conversion performed by the  CONVERT_TZ()  function. If the session time zone is UTC, there is effectively no time zone conversion.) Due to conventions for local time zone changes such as Daylight Saving Time (DST), conversions between UTC and non-UTC time zones are not one-to-one in both directions. UTC values that are distinct may not be distinct in another time zone. The following example shows distinct UTC values that become identical in a non-UTC time zone: 8.3.14 Indexed Lookups from TIMESTAMP Columns