Today discovered amazing website called W3SCHOOL, and there are many languages based tutorial is divided into a dignified short introduction, and combined with the example, it now appears still very effective for beginners, it intends to put the above sql learn about all of the relevant knowledge.
Some relatively special point about records sql learning today are as follows:
- There are differences in SQL DML and DDL, it is also because of this, only when there is something to delete delete and drop two kinds. Auxiliary memory!
- You can now order by the plurality of data columns, a first column of the system according to the first row, and then sorting results in its row according to the second column, and so on
- Note between different databases, processing between ... and ... when there will be the opening and closing range of different
