# UPDATE 语句

__*UPDATE 语法*__

+ 语法:
```10
UPDATE table_name ~!@SET col_name1=expression1@!~
  [,col_name2=expression2,...]
  [WHERE condition]
  [ORDER BY ...]
  [LIMIT row_count];

tidb> SELECT count(*) FROM universe.planets;
+----------+
| count(*) |
+----------+
|       10 |
+----------+

tidb> UPDATE universe.planets SET gravity = 0.0;
Query OK, 10 rows affected (0.01 sec)
Rows matched: 10  Changed: 10  Warnings: 0
```
-------------------------------------------------

除了赋值的子句部分,UPDATE 的其他字句语法和 SELECT 非常类似,本质上是找到已存在的表行,然后修改它们。如果你对 SELECT 语句不熟悉,请首先返回前导课程 201.2 Learn SQL from TiDB 进行学习。