1.SQL statement Category:
DQL data query, the SELECT
DML data manipulation statements, INSERT / the Delete / Update
DDL database definition language, the Create / drop / the ALTER
TCL transaction control statements, commit / rollback
2. Some statements
naming: as
fuzzy query: like
conditional query: where
default ascending: asc
descending: desc
3. The statement in the correct order
select ... from ... where ... group by ... having ... order by ...
4. Cross-table queries
across the table query has a phenomenon Cartesian product, i.e., the number of the query structure is the product of the number of two table element
5. Notes
DML statement update, needed to be added restrictions when delete operation or easy to make bulk changes to database
6. The three database design paradigm
first paradigm: the primary key, the field can be divided
second paradigm: the non-primary key field entirely dependent on the primary key
of the third paradigm: non-key fields can not be generated dependent on the primary key field transmitted
7. The characteristics of four things
atomicity, consistency, isolation, durability
8. The four things isolation levels (from low to high)
Read Uncommitted
Read Committed
Repeatable Read (MySQL default)
serialized
(This is written before, save for the draft, it is now made public, would add more detail later)