Oracle SQL经典SQL语句分享

--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
　　 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;