mysql句型积累

1. 统计数量（去重）
   SELECT COUNT(DISTINCT common_name) FROM drug;

2. load file

> load data local infile 'file_path' into table test_table 
> FIELDS TERMINATED BY '\t<FIELDS TERMINATED>\t' 
> ENCLOSED BY ” ESCAPED BY ”
> LINES TERMINATED BY '\n<LINES TERMINATED>\n'  
 > (field1，field2，field3，field4，field5，field6);

若数据中有反斜杠，需要指定 ESCAPED BY ”

3. mysql对json的支持
4. SELECT json_extract(obj, '$.name') FROM table_name WHERE field1 =0 and json_extract(json_field, '$.name') is not null;
5. update table_name set json_field = json_set(json_field, '$.country', '德国', '$.name', '乳糖') where id = 12505031;