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Merge pull request #195 from kwongtailau/master

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fix mispell, strongest compulsively
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CyC2018 2018-04-13 20:41:41 +08:00 committed by GitHub
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2 changed files with 7 additions and 7 deletions
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8
notes/SQL.md
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@ -251,7 +251,7 @@ FROM mytable
| LOWER() UPPER() | 转换为小写或者大写 |
| LTRIM() RTIM() | 去除左边或者右边的空格 |
| LENGTH() | 长度 |
| SUNDEX() | 转换为语音值 |
| SOUNDEX() | 转换为语音值 |
其中， **SOUNDEX()** 是将一个字符串转换为描述其语音表示的字母数字模式的算法，它是根据发音而不是字母比较。
@ -347,7 +347,7 @@ GROUP BY col
ORDER BY num;
```
WHERE 过滤行，HAVING 过滤分组。行过滤应当先与分组过滤；
WHERE 过滤行，HAVING 过滤分组。行过滤应当先于分组过滤；
```sql
SELECT col, COUNT(*) AS num
@ -464,7 +464,7 @@ from employee natural join department;
```sql
select Customers.cust_id, Orders.order_num
from Customers left outer join Orders
on Customers.cust_id = Orders.curt_id;
on Customers.cust_id = Orders.cust_id;
```
如果需要统计顾客的订单数，使用聚集函数。
@ -473,7 +473,7 @@ on Customers.cust_id = Orders.curt_id;
select Customers.cust_id,
COUNT(Orders.order_num) as num_ord
from Customers left outer join Orders
on Customers.cust_id = Orders.curt_id
on Customers.cust_id = Orders.cust_id
group by Customers.cust_id;
```

6
notes/数据库系统原理.md
View File

@ -227,13 +227,13 @@ MySQL 中提供了两种封锁粒度：行级锁以及表级锁。
事务遵循两段锁协议是保证并发操作可串行化调度的充分条件。例如以下操作满足两段锁协议，它是可串行化调度。
```html
lock-x(A)...lock-s(B)...lock-s(c)...unlock(A)...unlock(C)...unlock(B)
lock-x(A)...lock-s(B)...lock-s(C)...unlock(A)...unlock(C)...unlock(B)
```
但不是必要条件，例如以下操作不满足两段锁协议，但是它还是可串行化调度。
```html
lock-x(A)...unlock(A)...lock-s(B)...unlock(B)...lock-s(c)...unlock(C)...
lock-x(A)...unlock(A)...lock-s(B)...unlock(B)...lock-s(C)...unlock(C)...
```
# 四、隔离级别
@ -331,7 +331,7 @@ select * from table ....;
select * from table where ? lock in share mode;
select * from table where ? for update;
insert;
update ;
update;
delete;
```