MySQL-索引会加快我的搜索查询速度吗？

Question

I have a table for patients in a hospital, so potentially over time this table could contain tens of thousands of rows. A hospital-unique ID number (BIGINT) is assigned to each patient which serves as the PRIMARY KEY, and the rest of the columns are VARCHAR or CHAR, and a single DATE column. As far as I know, PRIMARY KEYS are automatically indexed so searching by the patient's ID is optimal(?).

Patients can be searched by a single field or a combination of this ID, name, address, date of birth etc. Can I optimize my search simply by creating an INDEX on each one of these fields? Would this optimization also work when a search is performed on a combination of these INDEXed fields such as

 SELECT * FROM patients WHERE first_name="John" AND address="blah blah blah";

???

Also, I presume MySQL uses its own internal algorithms for searching, perhaps binary search, and users cannot choose or implement their own?

Answer 1

From MySQL docs http://dev.mysql.com/doc/refman/5.0/en/mysql-indexes.html which is a pretty interesting read anyway:

Suppose that you issue the following SELECT statement:

mysql> SELECT * FROM tbl_name WHERE col1=val1 AND col2=val2;

If a multiple-column index exists on col1 and col2, the appropriate rows can be fetched directly. If separate single-column indexes exist on col1 and col2, the optimizer will attempt to use the Index Merge optimization (see