Exercise 2.49Use segments->painter to define the following primitive painters:a. The painter that draws the outline of the designated frame.
b. The painter that draws an “X” by connecting opposite corners of the frame.
c. The painter that draws a diam…
一、优化点:1、not in 替换为 not exist;2、in 替换为 right join;3、distinct 替换为 group by;4、count(distinct) 替换为 count;5、where条件中,等号左右两边的数据类型需要一致;6、where条件中,等号左边不要有函数;7、where条件上移;8、优化点需要对照执行计划,并…