RDBS何时使用复杂索引进行查询并何时使用简单？

Suppose I have table in my DB schema called TEST with fields (id, name, address, phone, comments). Now, I know that I'm going to perform a large set of different queries for that table, therefore my question is next, when and why I shall create indexes like ID_NAME_INDX (index for id and name) and when it's more efficient to create separately index for id and index for name field(by when I mean for what type of query)?Suppose I have table in my DB schema called TES