PK - Primary Key
IX - Non-Unique Index
AK - Unique Index (AX should have been AK (Alternate Key))
CK - Check Constraint
DF - Default Constraint
FK - Foreign Key
UK - Unique Key Constraint
SQL SERVER 索引名前缀代表的意思
原文：http://www.cnblogs.com/lfxiao/p/6760892.html
