一些有用的SQL语句

1.清空一张数据表
truncate table word(慎用) 

2.找出所有带有单引号的单词（单引号用两个单引号转义）
select * from Word where soundMarkUs like '%''%' 

3.调用replace函数将双引号替换成单引号
update Word  set soundMarkUs=REPLACE(soundMarkUs,'"','''') where soundMarkUs like'%"%'
  
4.备份一张数据表
select * into Course_bak from Course

5.显示一张表中去重之后的数据
select distinct spelling from Word

6.查询一张表中重复的数据
select * from Word where spelling in (select spelling from Word group by spelling having count(1) >= 2)

7.通过某个字段按字母顺序排序：ASC-升序(A-Z)；DESC-降序(Z-A)
select * from Word order by spelling asc
  
8.把字段数据类型由varchar改为nvarchar可以解决一些乱码的问题