删除约束时，支持索引也会被删除吗？

I am trying to memorize some sql syntax and I have gotten the ALTER TABLE ADD CONSTRAINT syntax down. I believe I am correct when I say that when you use this syntax to add a FOREIGN KEY or PRIMARY KEY constraint, that sql server automatically creates indexes to support the constraint operations. (Is that true...or is it only true on the PK but not the FK?)I am trying to memorize some sql syntax and I h