zoukankan      html  css  js  c++  java
  • Oracle: SQL精妙SQL语句讲解

    一、重复操作查询
    --where条件得distinct systemdicid作为唯一标识
    select *
    from dmis_zd_systemdic t
    WHERE typeid = '06012'
    and t.systemdicid in (select min(systemdicid)
    from dmis_zd_systemdic
    where typeid = '06012'
    group by name)
    order by orderno;
    二、检查表是否存在
    select count(tname) from tab where tname = upper('表名');
    三、日期函数
    --返回当前日期年度的第一天
    select trunc(sysdate,'year') from dual;
    --返回当前日期月份的第一天
    select trunc(sysdate,'month') from dual;
    --上月最后一天
    select last_day(add_months(sysdate, -1)) from dual;
    --给定日期后最近星期几得日期
    select next_day(to_date('2009-12-01', 'yyyy-mm-dd'), '星期一') next_day
    from dual;
    四、同一张表中,根据一个字段更新另一个字段
    update (select t.fgenerationtime as ftime, t.fgeneratedateall as str
    from dmis_fs_approvebook t
    where t.fgenerationtime is not null)
    set str = TO_CHAR(ftime, 'yyyy-mm-dd')
    where str is null;
    五、重复数据查询
    select * FROM EMP E
    WHERE E.ROWID > (SELECT MIN(X.ROWID)
    FROM EMP X
    WHERE X.EMP_NO = E.EMP_NO);
    六、合并不同表的数据(merge into
    merge into student s
    using (select id, name, tel from test001) x
    on (s.s_id = x.id)
    when matched then
    update set s_name = x.name
    when not matched then
    insert (s_id, s_name, s_age) values (x.id, x.name, x.tel);
    commit;
    七、查询执行sql(v$sql)
    select t.module, t.first_load_time, t.sql_text
    from v$sql t
    order by first_load_time desc;
    2、数据库精度修改处理
    -- Create table
    /*
    drop table temp_data;*/
    create table temp_data
    (
    FID VARCHAR2(40) not null,
    USEHOURS NUMBER(10) default 0,
    FVOLTAGE NUMBER(10) default 0,
    INVOLTAGE NUMBER(10) default 0
    )
    ;
    alter table TEMP_DATA
    add constraint tempfid primary key (FID);

    insert into temp_data
    select a.fid, a.usehours, a.fvoltage, a.involtage
    from dmis_fs_factorymonthdetail a;

    update dmis_fs_factorymonthdetail t
    set t.usehours = '', t.fvoltage = '', t.involtage = '';

    alter table DMIS_FS_FACTORYMONTHDETAIL modify USEHOURS NUMBER(10,1);
    alter table DMIS_FS_FACTORYMONTHDETAIL modify FVOLTAGE NUMBER(10,1);
    alter table DMIS_FS_FACTORYMONTHDETAIL modify INVOLTAGE NUMBER(10,1);

    update (select a.usehours as tusehours,
    b.usehours as fusehours,
    a.fvoltage as tfvoltage,
    b.fvoltage as ffvoltage,
    a.involtage as tinvoltage,
    b.involtage as finvoltage,
    a.fid as ffid,
    b.fid as tfid
    from dmis_fs_factorymonthdetail a, temp_data b
    where a.fid = b.fid) tt
    set tt.tusehours = tt.fusehours,
    tt.tfvoltage = tt.ffvoltage,
    tt.tinvoltage = tt.finvoltage
    where ffid = tfid;

    drop table temp_data;
    commit;

    3、恢复drop掉的存储过程
    用sys用户登陆,执行如下的查询:
    SQL> select text from dba_source as of timestamp to_timestamp('2009-03-06 09:45:00', 'YYYY-MM-DD HH24:MI:SS') where owner='IPRA' and name= 'P_IPACCHECK_NC' order by line;
    4、删除某个用户下的对象
    --删除某个用户下的对象
    set heading off;
    set feedback off;
    spool c:\dropobj.sql;
    prompt --Drop constraint
    select 'alter table '||table_name||' drop constraint '||constraint_name||' ;' from user_constraints where constraint_type='R';
    prompt --Drop tables
    select 'drop table '||table_name ||';' from user_tables;

    prompt --Drop view
    select 'drop view ' ||view_name||';' from user_views;

    prompt --Drop sequence
    select




    --行列转换 行转列
    DROP TABLE t_change_lc;
    CREATE TABLE t_change_lc (card_code VARCHAR2(3), q NUMBER, bal NUMBER);
    INSERT INTO t_change_lc
    SELECT '001' card_code, ROWNUM q, trunc(dbms_random.VALUE * 100) bal FROM dual CONNECT BY ROWNUM <= 4
    UNION
    SELECT '002' card_code, ROWNUM q, trunc(dbms_random.VALUE * 100) bal FROM dual CONNECT BY ROWNUM <= 4;
    SELECT * FROM t_change_lc;
    SELECT a.card_code,
    SUM(decode(a.q, 1, a.bal, 0)) q1,
    SUM(decode(a.q, 2, a.bal, 0)) q2,
    SUM(decode(a.q, 3, a.bal, 0)) q3,
    SUM(decode(a.q, 4, a.bal, 0)) q4
    FROM t_change_lc a
    GROUP BY a.card_code
    ORDER BY 1;

    --行列转换 列转行
    DROP TABLE t_change_cl;
    CREATE TABLE t_change_cl AS
    SELECT a.card_code,
    SUM(decode(a.q, 1, a.bal, 0)) q1,
    SUM(decode(a.q, 2, a.bal, 0)) q2,
    SUM(decode(a.q, 3, a.bal, 0)) q3,
    SUM(decode(a.q, 4, a.bal, 0)) q4
    FROM t_change_lc a
    GROUP BY a.card_code
    ORDER BY 1;
    SELECT * FROM t_change_cl;
    SELECT t.card_code,
    t.rn q,
    decode(t.rn, 1, t.q1, 2, t.q2, 3, t.q3, 4, t.q4) bal
    FROM (SELECT a.*, b.rn
    FROM t_change_cl a,
    (SELECT ROWNUM rn FROM dual CONNECT BY ROWNUM <= 4) b) t
    ORDER BY 1, 2;

    --行列转换 行转列 合并
    DROP TABLE t_change_lc_comma;
    CREATE TABLE t_change_lc_comma AS SELECT card_code,'quarter_'||q AS q FROM t_change_lc;
    SELECT * FROM t_change_lc_comma;
    SELECT t1.card_code, substr(MAX(sys_connect_by_path(t1.q, ';')), 2) q
    FROM (SELECT a.card_code,
    a.q,
    row_number() over(PARTITION BY a.card_code ORDER BY a.q) rn
    FROM t_change_lc_comma a) t1
    START WITH t1.rn = 1
    CONNECT BY t1.card_code = PRIOR t1.card_code
    AND t1.rn - 1 = PRIOR t1.rn
    GROUP BY t1.card_code;

    --行列转换 列转行 分割
    DROP TABLE t_change_cl_comma;
    CREATE TABLE t_change_cl_comma AS
    SELECT t1.card_code, substr(MAX(sys_connect_by_path(t1.q, ';')), 2) q
    FROM (SELECT a.card_code,
    a.q,
    row_number() over(PARTITION BY a.card_code ORDER BY a.q) rn
    FROM t_change_lc_comma a) t1
    START WITH t1.rn = 1
    CONNECT BY t1.card_code = PRIOR t1.card_code
    AND t1.rn - 1 = PRIOR t1.rn
    GROUP BY t1.card_code;
    SELECT * FROM t_change_cl_comma;
    SELECT t.card_code,
    substr(t.q,
    instr(';' || t.q, ';', 1, rn),
    instr(t.q || ';', ';', 1, rn) - instr(';' || t.q, ';', 1, rn)) q
    FROM (SELECT a.card_code, a.q, b.rn
    FROM t_change_cl_comma a,
    (SELECT ROWNUM rn FROM dual CONNECT BY ROWNUM <= 100) b
    WHERE instr(';' || a.q, ';', 1, rn) > 0) t
    ORDER BY 1, 2;

    -- 实现一条记录根据条件多表插入
    DROP TABLE t_ia_src;
    CREATE TABLE t_ia_src AS SELECT 'a'||ROWNUM c1, 'b'||ROWNUM c2 FROM dual CONNECT BY ROWNUM<=5;
    DROP TABLE t_ia_dest_1;
    CREATE TABLE t_ia_dest_1(flag VARCHAR2(10) , c VARCHAR2(10));
    DROP TABLE t_ia_dest_2;
    CREATE TABLE t_ia_dest_2(flag VARCHAR2(10) , c VARCHAR2(10));
    DROP TABLE t_ia_dest_3;
    CREATE TABLE t_ia_dest_3(flag VARCHAR2(10) , c VARCHAR2(10));
    SELECT * FROM t_ia_src;
    SELECT * FROM t_ia_dest_1;
    SELECT * FROM t_ia_dest_2;
    SELECT * FROM t_ia_dest_3;
    INSERT ALL
    WHEN (c1 IN ('a1','a3')) THEN
    INTO t_ia_dest_1(flag,c) VALUES(flag1,c2)
    WHEN (c1 IN ('a2','a4')) THEN
    INTO t_ia_dest_2(flag,c) VALUES(flag2,c2)
    ELSE
    INTO t_ia_dest_3(flag,c) VALUES(flag1||flag2,c1||c2)
    SELECT c1,c2, 'f1' flag1, 'f2' flag2 FROM t_ia_src;

    -- 如果存在就更新,不存在就插入用一个语句实现
    DROP TABLE t_mg;
    CREATE TABLE t_mg(code VARCHAR2(10), NAME VARCHAR2(10));
    SELECT * FROM t_mg;
    MERGE INTO t_mg a
    USING (SELECT 'the code' code, 'the name' NAME FROM dual) b
    ON (a.code = b.code)
    WHEN MATCHED THEN
    UPDATE SET a.NAME = b.NAME
    WHEN NOT MATCHED THEN
    INSERT (code, NAME) VALUES (b.code, b.NAME);

    -- 抽取/删除重复记录
    DROP TABLE t_dup;
    CREATE TABLE t_dup AS SELECT 'code_'||ROWNUM code, dbms_random.string('z',5) NAME FROM dual CONNECT BY ROWNUM<=10;
    INSERT INTO t_dup SELECT 'code_'||ROWNUM code, dbms_random.string('z',5) NAME FROM dual CONNECT BY ROWNUM<=2;
    SELECT * FROM t_dup;
    SELECT * FROM t_dup a WHERE a.ROWID <> (SELECT MIN(b.ROWID) FROM t_dup b WHERE a.code=b.code);
    SELECT b.code, b.NAME
    FROM (SELECT a.code,
    a.NAME,
    row_number() over(PARTITION BY a.code ORDER BY a.ROWID) rn
    FROM t_dup a) b
    WHERE b.rn > 1;
    -- IN/EXISTS的不同适用环境
    --
    t_orders.customer_id有索引
    SELECT a.*
    FROM t_employees a
    WHERE a.employee_id IN
    (SELECT b.sales_rep_id FROM t_orders b WHERE b.customer_id = 12);
    SELECT a.*
    FROM t_employees a
    WHERE EXISTS (SELECT 1
    FROM t_orders b
    WHERE b.customer_id = 12
    AND a.employee_id = b.sales_rep_id);
    -- t_employees.department_id有索引
    SELECT a.*
    FROM t_employees a
    WHERE a.department_id = 10
    AND EXISTS
    (SELECT 1 FROM t_orders b WHERE a.employee_id = b.sales_rep_id);
    SELECT a.*
    FROM t_employees a
    WHERE a.department_id = 10
    AND a.employee_id IN (SELECT b.sales_rep_id FROM t_orders b);
    -- FBI
    DROP TABLE t_fbi;
    CREATE TABLE t_fbi AS
    SELECT ROWNUM rn, dbms_random.STRING('z',10) NAME , SYSDATE + dbms_random.VALUE * 10 dt FROM dual
    CONNECT BY ROWNUM <=10;
    CREATE INDEX idx_nonfbi ON t_fbi(dt);
    DROP INDEX idx_fbi_1;
    CREATE INDEX idx_fbi_1 ON t_fbi(trunc(dt));
    SELECT * FROM t_fbi WHERE trunc(dt) = to_date('2006-09-21','yyyy-mm-dd') ;
    -- 不建议使用
    SELECT * FROM t_fbi WHERE to_char(dt, 'yyyy-mm-dd') = '2006-09-21';
    -- LOOP中的COMMIT/ROLLBACK
    DROP TABLE t_loop PURGE;
    create TABLE t_loop AS SELECT * FROM user_objects WHERE 1=2;
    SELECT * FROM t_loop;
    -- 逐行提交
    DECLARE
    BEGIN
    FOR cur IN (SELECT * FROM user_objects) LOOP
    INSERT INTO t_loop VALUES cur;
    COMMIT;
    END LOOP;
    END;

    -- 模拟批量提交
    DECLARE
    v_count NUMBER;
    BEGIN
    FOR cur IN (SELECT * FROM user_objects) LOOP
    INSERT INTO t_loop VALUES cur;
    v_count := v_count + 1;
    IF v_count >= 100 THEN
    COMMIT;
    END IF;
    END LOOP;
    COMMIT;
    END;

    -- 真正的批量提交
    DECLARE
    CURSOR cur IS
    SELECT * FROM user_objects;
    TYPE rec IS TABLE OF user_objects%ROWTYPE;
    recs rec;
    BEGIN
    OPEN cur;
    WHILE (TRUE) LOOP
    FETCH cur BULK COLLECT
    INTO recs LIMIT 100;

    -- forall 实现批量
    FORALL i IN 1 .. recs.COUNT
    INSERT INTO t_loop VALUES recs (i);
    COMMIT;
    EXIT WHEN cur%NOTFOUND;
    END LOOP;
    CLOSE cur;
    END;

    -- 悲观锁定/乐观锁定
    DROP TABLE t_lock PURGE;
    CREATE TABLE t_lock AS SELECT 1 ID FROM dual;
    SELECT * FROM t_lock;

    -- 常见的实现逻辑,隐含bug
    DECLARE
    v_cnt NUMBER;
    BEGIN

    -- 这里有并发性的bug
    SELECT MAX(ID) INTO v_cnt FROM t_lock;
    -- here for other operation
    v_cnt := v_cnt + 1;
    INSERT INTO t_lock (ID) VALUES (v_cnt);
    COMMIT;
    END;

    -- 高并发环境下,安全的实现逻辑
    DECLARE
    v_cnt NUMBER;
    BEGIN

    -- 对指定的行取得lock
    SELECT ID INTO v_cnt FROM t_lock WHERE ID=1 FOR UPDATE;

    -- 在有lock的情况下继续下面的操作
    SELECT MAX(ID) INTO v_cnt FROM t_lock;
    -- here for other operation
    v_cnt := v_cnt + 1;
    INSERT INTO t_lock (ID) VALUES (v_cnt);
    COMMIT; --提交并且释放lock
    END;

    -- 硬解析/软解析
    DROP TABLE t_hard PURGE;
    CREATE TABLE t_hard (ID INT);
    SELECT * FROM t_hard;
    DECLARE
    sql_1 VARCHAR2(200);
    BEGIN
    -- hard parse
    --
    java中的同等语句是 Statement.execute()
    FOR i IN 1 .. 1000 LOOP
    sql_1 := 'insert into t_hard(id) values(' || i || ')';
    EXECUTE IMMEDIATE sql_1;
    END LOOP;
    COMMIT;
    -- soft parse
    --
    java中的同等语句是 PreparedStatement.execute()
    sql_1 := 'insert into t_hard(id) values(:id)';
    FOR i IN 1 .. 1000 LOOP
    EXECUTE IMMEDIATE sql_1
    USING i;
    END LOOP;
    COMMIT;
    END;

    -- 正确的分页算法
    SELECT *
    FROM (SELECT a.*, ROWNUM rn
    FROM (SELECT * FROM t_employees ORDER BY first_name) a
    WHERE ROWNUM <= 500)
    WHERE rn > 480 ;

    -- 分页算法(why not this one)
    SELECT a.*, ROWNUM rn
    FROM (SELECT * FROM t_employees ORDER BY first_name) a
    WHERE ROWNUM <= 500 AND ROWNUM > 480;

    -- 分页算法(why not this one)
    SELECT b.*
    FROM (SELECT a.*, ROWNUM rn
    FROM t_employees a
    WHERE ROWNUM < = 500
    ORDER BY first_name) b
    WHERE b.rn > 480;
    -- OLAP

    -- 小计合计
    SELECT CASE
    WHEN a.deptno IS NULL THEN
    '合计'
    WHEN a.deptno IS NOT NULL AND a.empno IS NULL THEN
    '小计'
    ELSE
    '' || a.deptno
    END deptno,
    a.empno,
    a.ename,
    SUM(a.sal) total_sal
    FROM scott.emp a
    GROUP BY GROUPING SETS((a.deptno),(a.deptno, a.empno, a.ename),());

    -- 分组排序
    SELECT a.deptno,
    a.empno,
    a.ename,
    a.sal,
    -- 可跳跃的rank
    rank() over(PARTITION BY a.deptno ORDER BY a.sal DESC) r1,
    -- 密集型rank
    dense_rank() over(PARTITION BY a.deptno ORDER BY a.sal DESC) r2,
    -- 不分组排序
    rank() over(ORDER BY sal DESC) r3
    FROM scott.emp a
    ORDER BY a.deptno,a.sal DESC;
    -- 当前行数据和前/后n行的数据比较
    SELECT a.empno,
    a.ename,
    a.sal,
    -- 上面一行
    lag(a.sal) over(ORDER BY a.sal DESC) lag_1,
    -- 下面三行
    lead(a.sal, 3) over(ORDER BY a.sal DESC) lead_3
    FROM scott.emp a
    ORDER BY a.sal DESC;


    编辑器加载中...

    魔兽就是毒瘤,大家千万不要玩。
  • 相关阅读:
    Android 摇一摇之双甩功能
    Android 上千张图片的列表滑动加载
    Android 新手引导
    Android 自定义列表指示器
    Mininet的安装与卸载
    ubuntu装机必备
    linux系统中利用vagrant创建虚拟开发环境
    Ubuntu右键添加:open in terminal
    ryu启动问题总结
    新建WORD文档打开会出现转换文件对话框3步解决办法
  • 原文地址:https://www.cnblogs.com/tracy/p/2270656.html
Copyright © 2011-2022 走看看