Three tables LEFT JOIN query SQL statement Writing _ database other

Today I want to check all the Realname Username,psw,gname,tel
Table structure:
Table T1
Field Name: T1_ID,USERNAME,PSW
Table T2
Field Name: t2_id,gname,t1_id//Here a t1_id corresponds to multiple t2_id
T3
Field Name: t3_id,realname,tel,t1_id//Here a t1_id corresponds to a t3_id
The trouble is when a realname in the T2 table does not have content, but also to the Username,psw,tel of this realname display, direct use
Sql= "Select Username,psw,gname,tel from T1,t2,t3 where t1.t1_id=t2.t1_id and t1.t1_id=t3.t1_id"
The result is: T2 table must have a realname work, in order to query out his information, this is certainly not the desired result, finally thought of using the left connection, the SQL statement is:
Sql= "Select Username,psw,gname,tel from (T1 left join T2 on t1.t1_id=t2.t1_id) left join T3 on t1.t1_id=t3.t1_id"
This will result in the desired results.