分页查询，order by，where用法

一、
//查询数据库ESS的Elog表格的ETime、Des列
//查询出的结果只显示这两列
SELECT E_LOG."ETime", E_LOG."Des", ROWNUM rn
FROM ESS."E_LOG"

二、
//分页查询ROWNUM 用法
//rn变量，行号，只查询返回结果表（1）的第0行到第30000行
SELECT * FROM (
    SELECT E_LOG."ETime", E_LOG."Des", ROWNUM rn
    FROM ESS."E_LOG"
) WHERE rn BETWEEN 0 AND 30000;

三、
//1、where用法
//只返回结果ETime列的DATE类型的值在这个区间的记录
//2、TO_DATE函数用法，可自定义时间，以及格式，只有年、有年月、有年月日、年月日时分秒，都可
实例1：
SELECT * FROM (
    SELECT E_LOG."ETime", E_LOG."Des", ROWNUM rn
    FROM ESS."E_LOG"
		WHERE "ETime" BETWEEN TO_DATE('2022-11-30', 'YYYY-MM-DD') AND TO_DATE('2023-12-20', 'YYYY-MM-DD')
) WHERE rn BETWEEN 0 AND 30000;
实例2：
SELECT * FROM (
    SELECT E_LOG."ETime", E_LOG."Des", E_LOG."StnName",ROWNUM rn
    FROM ESS."E_LOG"
		WHERE "ETime" BETWEEN TO_DATE('2022-11-30 09:44:23', 'yyyy-mm-dd HH24:mi:ss') AND TO_DATE('2023-12-20 13:39:00', 'yyyy-mm-dd HH24:mi:ss')
) WHERE rn BETWEEN 0 AND 30000;

SELECT * FROM (
    SELECT E_LOG."ETime", E_LOG."Des", ROWNUM rn
    FROM ESS."E_LOG"
		WHERE "ETime" BETWEEN TO_DATE('2022-11-30 09:44:23', 'yyyy-mm-dd HH24:mi:ss') AND TO_DATE('2023-12-20 13:39:00', 'yyyy-mm-dd HH24:mi:ss')
		ORDER BY "ETime"
) WHERE rn BETWEEN 0 AND 30000;

SELECT * FROM (
    SELECT E_LOG."ETime", E_LOG."Des", ROWNUM rn
    FROM ESS."E_LOG"
		WHERE "ETime" BETWEEN TO_DATE('2022-11-30', 'YYYY-MM-DD') AND TO_DATE('2023-12-20', 'YYYY-MM-DD')
		ORDER BY "ETime"
) WHERE rn BETWEEN 0 AND 30000;

四、
//分页查询，另一种方法OFFSET n从第n行开始
//fetch next rows only只查从第几行开始的rows行记录
SELECT COUNT(*) FROM ESS.E_LOG;

SELECT E_LOG."ETime", E_LOG."ELevel"
FROM ESS.E_LOG
WHERE "Type"=160
OFFSET 0 ROWS
FETCH NEXT 30000 ROWS ONLY;