Mysql-DBA--20220523 資料型別(續)
阿新 • • 發佈:2022-05-23
13、字串型別--ENUM&SET
14、日期型別
15、幾個時間函式
- ([email protected])[mysql]> select now();
- ([email protected])[mysql]> select unix_timestamp(now());
- ([email protected])[mysql]> select now(6);
- now(6):6位毫秒
- now(3):3位毫秒
- ([email protected])[mysql]> select now(),sysdate(),sleep(5),now(),sysdate();
-
注意:now和sysdate的區別
-
注意:now和sysdate的區別
- ([email protected])[mysql]> select now(6),sysdate(6);
- 注意:毫秒數不同。
- now:執行這條select語句的時間。
- sysdate:執行到sysdate()函式時的時間。
- ([email protected])[mysql]> select date_add(now(),interval 1 day);
- ([email protected])[mysql]> select date_add(now(),interval -1 day);
- ([email protected])[mysql]> select date_add(now(),interval -1 hour);
- ([email protected])[mysql]> select date_format(now(),'%Y%m%d');
- 可以各種格式:date_format(now(),'%Y-%m-%d'),date_format(now(),'%Y_%m_%d')
- 注意:等號左邊,不建議用date_format函式。因為用不到索引了。效率低下。
16、JSON型別
17、幾個函式
- ([email protected])[test]> create table userJson (uid int auto_increment primary key, data json);
- ([email protected])[test]> insert into userjson values(null, {"name":"lijf","address":"shanghai"});
- ([email protected])[test]> select * from userjson;
- ([email protected])[test]> select uid,json_extract(data,"$.name") from userjson;
- ([email protected])[test]> select uid,json_unquote(json_extract(data,"$.name")) from userjson;
- ([email protected])[test]> select uid, data->>"$.name" from userjson;
- ([email protected])[test]> select uid, data->"$.name" from userjson;