EXPLAIN Table reference order

[Sunil H]

Hi,
I have two cases for Explain. I have added additional where condition [AND T2.city='Banglore'] in the case 2 and I want to know why the order of table reference gets changed in the case 2.

CASE 1:
EXPLAIN select count(*) from exp1 AS T1 JOIN exp2 AS T2 ON T1.ip=T2.ip WHERE (T1.severity LIKE ('critical%') AND (T2.main="All" OR T2.state="All" OR T2.city="All" OR T2.ip="All")) \G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: T1
type: range
possible_keys: ip,severity
key: severity
key_len: 258
ref: NULL
rows: 1
Extra: Using where
*************************** 2. row ***************************
id: 1
select_type: SIMPLE
table: T2
type: ref
possible_keys: state,city,ip,main
key: ip
key_len: 258
ref: telsimaDB1_3.T1.ip
rows: 2
Extra: Using where
2 rows in set (0.00 sec)
----------------------------------------------------------------------------------

CASE 2:
explain select count(*) from exp1 AS T1 JOIN exp2 AS T2 ON T1.ip=T2.ip WHERE (T1.severity LIKE ('critical%') AND (T2.main="All" OR T2.state="All" OR T2.city="All" OR T2.ip="All") AND T2.city='Banglore') \G
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: T2
type: ref
possible_keys: state,city,ip,main
key: city
key_len: 258
ref: const
rows: 1
Extra: Using where
*************************** 2. row ***************************
id: 1
select_type: SIMPLE
table: T1
type: ref
possible_keys: ip,severity
key: ip
key_len: 258
ref: telsimaDB1_3.T2.ip
rows: 2
Extra: Using where
2 rows in set (0.00 sec)



Thanks,
Sunil