This chapter will help you to get answers on typical interview questions for developers who use databases in work.
MyISAM allow to create full-text search index, but doesn't have support of transactions and foreign keys.
InnoDB supports transations and foreign keys.
Composite key is used if we need to create index based on two or more columns. If we need to search by first column from composite key - we don't need to create additional index. But for all other columns that follow after this first column - we need to create additonal indexes.
For example, we have table users with 3 columns: name, age and company_name. We have composite key for all 3 columns KEY (name, age, company_name). In this case we can search user by name OR by name and age OR by name, age and company_name. But we can't search by age or company_name because index should find name before go forward to search by next column. To search by age or company_name we need to create an additonal index.