如果你只是尋求多行轉(zhuǎn)換成一列，比如把同一個id的某個字段col變成一行數(shù)據(jù)庫，把多個col用逗號鏈接起來。下面幾個SQL可以立竿見影。
1.
概述
最近論壇很多人提的問題都與行列轉(zhuǎn)換有關(guān)系，所以我對行列轉(zhuǎn)換的相關(guān)知識做了一個總結(jié)，希望對大家有所幫助，同時有何錯疏，懇請大家指出，我也是在寫作過程中學(xué)習(xí)，算是一起和大家學(xué)習(xí)吧！
行列轉(zhuǎn)換包括以下六種情況：
1)
列轉(zhuǎn)行
2)
行轉(zhuǎn)列
3)
多列轉(zhuǎn)換成字符串
4)
多行轉(zhuǎn)換成字符串
5)
字符串轉(zhuǎn)換成多列
6)
字符串轉(zhuǎn)換成多行
下面分別進行舉例介紹。
首先聲明一點，有些例子需要如下10g及以后才有的知識：
A.
掌握model子句
B.
正則表達式
C.
加強的層次查詢
討論的適用范圍只包括8i,9i,10g及以后版本。
2.
列轉(zhuǎn)行
CREATE TABLE t_col_row(
ID INT,
c1 VARCHAR2(10),
c2 VARCHAR2(10),
c3 VARCHAR2(10));
INSERT INTO t_col_row VALUES (1, 'v11', 'v21', 'v31');
INSERT INTO t_col_row VALUES (2, 'v12', 'v22', NULL);
INSERT INTO t_col_row VALUES (3, 'v13', NULL, 'v33');
INSERT INTO t_col_row VALUES (4, NULL, 'v24', 'v34');
INSERT INTO t_col_row VALUES (5, 'v15', NULL, NULL);
INSERT INTO t_col_row VALUES (6, NULL, NULL, 'v35');
INSERT INTO t_col_row VALUES (7, NULL, NULL, NULL);
COMMIT;
SELECT * FROM t_col_row;
2.1
UNION ALL
適用范圍：8i,9i,10g及以后版本
SELECT id, 'c1' cn, c1 cv
FROM t_col_row
UNION ALL
SELECT id, 'c2' cn, c2 cv
FROM t_col_row
UNION ALL
SELECT id, 'c3' cn, c3 cv FROM t_col_row;
若空行不需要轉(zhuǎn)換，只需加一個where條件，
WHERE COLUMN IS NOT NULL 即可。
2.2
MODEL
適用范圍：10g及以后
SELECT id, cn, cv FROM t_col_row
MODEL
RETURN UPDATED ROWS
PARTITION BY (ID)
DIMENSION BY (0 AS n)
MEASURES ('xx' AS cn,'yyy' AS cv,c1,c2,c3)
RULES UPSERT ALL
(
cn[1] = 'c1',
cn[2] = 'c2',
cn[3] = 'c3',
cv[1] = c1[0],
cv[2] = c2[0],
cv[3] = c3[0]
)
ORDER BY ID,cn;
2.3
COLLECTION
適用范圍：8i,9i,10g及以后版本
要創(chuàng)建一個對象和一個集合：
CREATE TYPE cv_pair AS OBJECT(cn VARCHAR2(10),cv VARCHAR2(10));
CREATE TYPE cv_varr AS VARRAY(8) OF cv_pair;
SELECT id, t.cn AS cn, t.cv AS cv
FROM t_col_row,
TABLE(cv_varr(cv_pair('c1', t_col_row.c1),
cv_pair('c2', t_col_row.c2),
cv_pair('c3', t_col_row.c3))) t
ORDER BY 1, 2;
3.
行轉(zhuǎn)列
CREATE TABLE t_row_col AS
SELECT id, 'c1' cn, c1 cv
FROM t_col_row
UNION ALL
SELECT id, 'c2' cn, c2 cv
FROM t_col_row
UNION ALL
SELECT id, 'c3' cn, c3 cv FROM t_col_row;
SELECT * FROM t_row_col ORDER BY 1,2;
3.1
AGGREGATE FUNCTION
適用范圍：8i,9i,10g及以后版本
SELECT id,
MAX(decode(cn, 'c1', cv, NULL)) AS c1,
MAX(decode(cn, 'c2', cv, NULL)) AS c2,
MAX(decode(cn, 'c3', cv, NULL)) AS c3
FROM t_row_col
GROUP BY id
ORDER BY 1;
MAX聚集函數(shù)也可以用sum、min、avg等其他聚集函數(shù)替代。
被指定的轉(zhuǎn)置列只能有一列，但固定的列可以有多列，請看下面的例子：
SELECT mgr, deptno, empno, ename FROM emp ORDER BY 1, 2;
SELECT mgr,
deptno,
MAX(decode(empno, '7788', ename, NULL)) "7788",
MAX(decode(empno, '7902', ename, NULL)) "7902",
MAX(decode(empno, '7844', ename, NULL)) "7844",
MAX(decode(empno, '7521', ename, NULL)) "7521",
MAX(decode(empno, '7900', ename, NULL)) "7900",
MAX(decode(empno, '7499', ename, NULL)) "7499",
MAX(decode(empno, '7654', ename, NULL)) "7654"
FROM emp
WHERE mgr IN (7566, 7698)
AND deptno IN (20, 30)
GROUP BY mgr, deptno
ORDER BY 1, 2;
這里轉(zhuǎn)置列為empno，固定列為mgr，deptno。
還有一種行轉(zhuǎn)列的方式，就是相同組中的行值變?yōu)閱蝹€列值，但轉(zhuǎn)置的行值不變?yōu)榱忻?br style="word-wrap: break-word" />ID CN_1 CV_1 CN_2 CV_2 CN_3 CV_3
1 c1 v11 c2 v21 c3 v31
2 c1 v12 c2 v22 c3
3 c1 v13 c2 c3 v33
4 c1 c2 v24 c3 v34
5 c1 v15 c2 c3
6 c1 c2 c3 v35
7 c1 c2 c3
這種情況可以用分析函數(shù)實現(xiàn)：
SELECT id,
MAX(decode(rn, 1, cn, NULL)) cn_1,
MAX(decode(rn, 1, cv, NULL)) cv_1,
MAX(decode(rn, 2, cn, NULL)) cn_2,
MAX(decode(rn, 2, cv, NULL)) cv_2,
MAX(decode(rn, 3, cn, NULL)) cn_3,
MAX(decode(rn, 3, cv, NULL)) cv_3
FROM (SELECT id,
cn,
cv,
row_number() over(PARTITION BY id ORDER BY cn, cv) rn
FROM t_row_col)
GROUP BY ID;
3.2
PL/SQL
適用范圍：8i,9i,10g及以后版本
這種對于行值不固定的情況可以使用。
下面是我寫的一個包，包中
p_rows_column_real用于前述的第一種不限定列的轉(zhuǎn)換；
p_rows_column用于前述的第二種不限定列的轉(zhuǎn)換。
CREATE OR REPLACE PACKAGE pkg_dynamic_rows_column AS
TYPE refc IS REF CURSOR;
PROCEDURE p_print_sql(p_txt VARCHAR2);
FUNCTION f_split_str(p_str VARCHAR2, p_division VARCHAR2, p_seq INT)
RETURN VARCHAR2;
PROCEDURE p_rows_column(p_table IN VARCHAR2,
p_keep_cols IN VARCHAR2,
p_pivot_cols IN VARCHAR2,
p_where IN VARCHAR2 DEFAULT NULL,
p_refc IN OUT refc);
PROCEDURE p_rows_column_real(p_table IN VARCHAR2,
p_keep_cols IN VARCHAR2,
p_pivot_col IN VARCHAR2,
p_pivot_val IN VARCHAR2,
p_where IN VARCHAR2 DEFAULT NULL,
p_refc IN OUT refc);
END;
/
CREATE OR REPLACE PACKAGE BODY pkg_dynamic_rows_column AS
PROCEDURE p_print_sql(p_txt VARCHAR2) IS
v_len INT;
BEGIN
v_len := length(p_txt);
FOR i IN 1 .. v_len / 250 + 1 LOOP
dbms_output.put_line(substrb(p_txt, (i - 1) * 250 + 1, 250));
END LOOP;
END;
FUNCTION f_split_str(p_str VARCHAR2, p_division VARCHAR2, p_seq INT)
RETURN VARCHAR2 IS
v_first INT;
v_last INT;
BEGIN
IF p_seq < 1 THEN
RETURN NULL;
END IF;
IF p_seq = 1 THEN
IF instr(p_str, p_division, 1, p_seq) = 0 THEN
RETURN p_str;
ELSE
RETURN substr(p_str, 1, instr(p_str, p_division, 1) - 1);
END IF;
ELSE
v_first := instr(p_str, p_division, 1, p_seq - 1);
v_last := instr(p_str, p_division, 1, p_seq);
IF (v_last = 0) THEN
IF (v_first > 0) THEN
RETURN substr(p_str, v_first + 1);
ELSE
RETURN NULL;
END IF;
ELSE
RETURN substr(p_str, v_first + 1, v_last - v_first - 1);
END IF;
END IF;
END f_split_str;
PROCEDURE p_rows_column(p_table IN VARCHAR2,
p_keep_cols IN VARCHAR2,
p_pivot_cols IN VARCHAR2,
p_where IN VARCHAR2 DEFAULT NULL,
p_refc IN OUT refc) IS
v_sql VARCHAR2(4000);
TYPE v_keep_ind_by IS TABLE OF VARCHAR2(4000) INDEX BY BINARY_INTEGER;
v_keep v_keep_ind_by;
TYPE v_pivot_ind_by IS TABLE OF VARCHAR2(4000) INDEX BY BINARY_INTEGER;
v_pivot v_pivot_ind_by;
v_keep_cnt INT;
v_pivot_cnt INT;
v_max_cols INT;
v_partition VARCHAR2(4000);
v_partition1 VARCHAR2(4000);
v_partition2 VARCHAR2(4000);
BEGIN
v_keep_cnt := length(p_keep_cols) - length(REPLACE(p_keep_cols, ',')) + 1;
v_pivot_cnt := length(p_pivot_cols) -
length(REPLACE(p_pivot_cols, ',')) + 1;
FOR i IN 1 .. v_keep_cnt LOOP
v_keep(i) := f_split_str(p_keep_cols, ',', i);
END LOOP;
FOR j IN 1 .. v_pivot_cnt LOOP
v_pivot(j) := f_split_str(p_pivot_cols, ',', j);
END LOOP;
v_sql := 'select max(count(*)) from ' || p_table || ' group by ';
FOR i IN 1 .. v_keep.LAST LOOP
v_sql := v_sql || v_keep(i) || ',';
END LOOP;
v_sql := rtrim(v_sql, ',');
EXECUTE IMMEDIATE v_sql
INTO v_max_cols;
v_partition := 'select ';
FOR x IN 1 .. v_keep.COUNT LOOP
v_partition1 := v_partition1 || v_keep(x) || ',';
END LOOP;
FOR y IN 1 .. v_pivot.COUNT LOOP
v_partition2 := v_partition2 || v_pivot(y) || ',';
END LOOP;
v_partition1 := rtrim(v_partition1, ',');
v_partition2 := rtrim(v_partition2, ',');
v_partition := v_partition || v_partition1 || ',' || v_partition2 ||
', row_number() over (partition by ' || v_partition1 ||
' order by ' || v_partition2 || ') rn from ' || p_table;
v_partition := rtrim(v_partition, ',');
v_sql := 'select ';
FOR i IN 1 .. v_keep.COUNT LOOP
v_sql := v_sql || v_keep(i) || ',';
END LOOP;
FOR i IN 1 .. v_max_cols LOOP
FOR j IN 1 .. v_pivot.COUNT LOOP
v_sql := v_sql || ' max(decode(rn,' || i || ',' || v_pivot(j) ||
',null))' || v_pivot(j) || '_' || i || ',';
END LOOP;
END LOOP;
IF p_where IS NOT NULL THEN
v_sql := rtrim(v_sql, ',') || ' from (' || v_partition || ' ' ||
p_where || ') group by ';
ELSE
v_sql := rtrim(v_sql, ',') || ' from (' || v_partition ||
') group by ';
END IF;
FOR i IN 1 .. v_keep.COUNT LOOP
v_sql := v_sql || v_keep(i) || ',';
END LOOP;
v_sql := rtrim(v_sql, ',');
p_print_sql(v_sql);
OPEN p_refc FOR v_sql;
EXCEPTION
WHEN OTHERS THEN
OPEN p_refc FOR
SELECT 'x' FROM dual WHERE 0 = 1;
END;
PROCEDURE p_rows_column_real(p_table IN VARCHAR2,
p_keep_cols IN VARCHAR2,
p_pivot_col IN VARCHAR2,
p_pivot_val IN VARCHAR2,
p_where IN VARCHAR2 DEFAULT NULL,
p_refc IN OUT refc) IS
v_sql VARCHAR2(4000);
TYPE v_keep_ind_by IS TABLE OF VARCHAR2(4000) INDEX BY BINARY_INTEGER;
v_keep v_keep_ind_by;
TYPE v_pivot_ind_by IS TABLE OF VARCHAR2(4000) INDEX BY BINARY_INTEGER;
v_pivot v_pivot_ind_by;
v_keep_cnt INT;
v_group_by VARCHAR2(2000);
BEGIN
v_keep_cnt := length(p_keep_cols) - length(REPLACE(p_keep_cols, ',')) + 1;
FOR i IN 1 .. v_keep_cnt LOOP
v_keep(i) := f_split_str(p_keep_cols, ',', i);
END LOOP;
v_sql := 'select ' || 'cast(' || p_pivot_col ||
' as varchar2(200)) as ' || p_pivot_col || ' from ' || p_table ||
' group by ' || p_pivot_col;
EXECUTE IMMEDIATE v_sql BULK COLLECT
INTO v_pivot;
FOR i IN 1 .. v_keep.COUNT LOOP
v_group_by := v_group_by || v_keep(i) || ',';
END LOOP;
v_group_by := rtrim(v_group_by, ',');
v_sql := 'select ' || v_group_by || ',';
FOR x IN 1 .. v_pivot.COUNT LOOP
v_sql := v_sql || ' max(decode(' || p_pivot_col || ',' || chr(39) ||
v_pivot(x) || chr(39) || ',' || p_pivot_val ||
',null)) as "' || v_pivot(x) || '",';
END LOOP;
v_sql := rtrim(v_sql, ',');
IF p_where IS NOT NULL THEN
v_sql := v_sql || ' from ' || p_table || p_where || ' group by ' ||
v_group_by;
ELSE
v_sql := v_sql || ' from ' || p_table || ' group by ' || v_group_by;
END IF;
p_print_sql(v_sql);
OPEN p_refc FOR v_sql;
EXCEPTION
WHEN OTHERS THEN
OPEN p_refc FOR
SELECT 'x' FROM dual WHERE 0 = 1;
END;
END;
/
4.
多列轉(zhuǎn)換成字符串
CREATE TABLE t_col_str AS
SELECT * FROM t_col_row;
這個比較簡單，用||或concat函數(shù)可以實現(xiàn)：
SELECT concat('a','b') FROM dual;
4.1
|| OR CONCAT
適用范圍：8i,9i,10g及以后版本
SELECT * FROM t_col_str;
SELECT ID,c1||','||c2||','||c3 AS c123
FROM t_col_str;
5.
多行轉(zhuǎn)換成字符串
CREATE TABLE t_row_str(
ID INT,
col VARCHAR2(10));
INSERT INTO t_row_str VALUES(1,'a');
INSERT INTO t_row_str VALUES(1,'b');
INSERT INTO t_row_str VALUES(1,'c');
INSERT INTO t_row_str VALUES(2,'a');
INSERT INTO t_row_str VALUES(2,'d');
INSERT INTO t_row_str VALUES(2,'e');
INSERT INTO t_row_str VALUES(3,'c');
COMMIT;
SELECT * FROM t_row_str;
5.1
MAX + DECODE
適用范圍：8i,9i,10g及以后版本
SELECT id,
MAX(decode(rn, 1, col, NULL)) ||
MAX(decode(rn, 2, ',' || col, NULL)) ||
MAX(decode(rn, 3, ',' || col, NULL)) str
FROM (SELECT id,
col,
row_number() over(PARTITION BY id ORDER BY col) AS rn
FROM t_row_str) t
GROUP BY id
ORDER BY 1;
5.2
ROW_NUMBER + LEAD
適用范圍：8i,9i,10g及以后版本
SELECT id, str
FROM (SELECT id,
row_number() over(PARTITION BY id ORDER BY col) AS rn,
col || lead(',' || col, 1) over(PARTITION BY id ORDER BY col) ||
lead(',' || col, 2) over(PARTITION BY id ORDER BY col) ||
lead(',' || col, 3) over(PARTITION BY id ORDER BY col) AS str
FROM t_row_str)
WHERE rn = 1
ORDER BY 1;
5.3
MODEL
適用范圍：10g及以后版本
SELECT id, substr(str, 2) str FROM t_row_str
MODEL
RETURN UPDATED ROWS
PARTITION BY(ID)
DIMENSION BY(row_number() over(PARTITION BY ID ORDER BY col) AS rn)
MEASURES (CAST(col AS VARCHAR2(20)) AS str)
RULES UPSERT
ITERATE(3) UNTIL( presentv(str[iteration_number+2],1,0)=0)
(str[0] = str[0] || ',' || str[iteration_number+1])
ORDER BY 1;
5.4
SYS_CONNECT_BY_PATH
適用范圍：8i,9i,10g及以后版本
SELECT t.id id, MAX(substr(sys_connect_by_path(t.col, ','), 2)) str
FROM (SELECT id, col, row_number() over(PARTITION BY id ORDER BY col) rn
FROM t_row_str) t
START WITH rn = 1
CONNECT BY rn = PRIOR rn + 1
AND id = PRIOR id
GROUP BY t.id;
適用范圍：10g及以后版本
SELECT t.id id, substr(sys_connect_by_path(t.col, ','), 2) str
FROM (SELECT id, col, row_number() over(PARTITION BY id ORDER BY col) rn
FROM t_row_str) t
WHERE connect_by_isleaf = 1
START WITH rn = 1
CONNECT BY rn = PRIOR rn + 1
AND id = PRIOR id;
5.5
WMSYS.WM_CONCAT
適用范圍：10g及以后版本
這個函數(shù)預(yù)定義按','分隔字符串，若要用其他符號分隔可以用，replace將','替換。
SELECT id, REPLACE(wmsys.wm_concat(col), ',', '/') str
FROM t_row_str
GROUP BY id;
6.
字符串轉(zhuǎn)換成多列
其實際上就是一個字符串拆分的問題。
CREATE TABLE t_str_col AS
SELECT ID,c1||','||c2||','||c3 AS c123
FROM t_col_str;
SELECT * FROM t_str_col;
6.1
SUBSTR + INSTR
適用范圍：8i,9i,10g及以后版本
SELECT id,
c123,
substr(c123, 1, instr(c123 || ',', ',', 1, 1) - 1) c1,
substr(c123,
instr(c123 || ',', ',', 1, 1) + 1,
instr(c123 || ',', ',', 1, 2) - instr(c123 || ',', ',', 1, 1) - 1) c2,
substr(c123,
instr(c123 || ',', ',', 1, 2) + 1,
instr(c123 || ',', ',', 1, 3) - instr(c123 || ',', ',', 1, 2) - 1) c3
FROM t_str_col
ORDER BY 1;
6.2
REGEXP_SUBSTR
適用范圍：10g及以后版本
SELECT id,
c123,
rtrim(regexp_substr(c123 || ',', '.*?' || ',', 1, 1), ',') AS c1,
rtrim(regexp_substr(c123 || ',', '.*?' || ',', 1, 2), ',') AS c2,
rtrim(regexp_substr(c123 || ',', '.*?' || ',', 1, 3), ',') AS c3
FROM t_str_col
ORDER BY 1;
7.
字符串轉(zhuǎn)換成多行
CREATE TABLE t_str_row AS
SELECT id,
MAX(decode(rn, 1, col, NULL)) ||
MAX(decode(rn, 2, ',' || col, NULL)) ||
MAX(decode(rn, 3, ',' || col, NULL)) str
FROM (SELECT id,
col,
row_number() over(PARTITION BY id ORDER BY col) AS rn
FROM t_row_str) t
GROUP BY id
ORDER BY 1;
SELECT * FROM t_str_row;
7.1
UNION ALL
適用范圍：8i,9i,10g及以后版本
SELECT id, 1 AS p, substr(str, 1, instr(str || ',', ',', 1, 1) - 1) AS cv
FROM t_str_row
UNION ALL
SELECT id,
2 AS p,
substr(str,
instr(str || ',', ',', 1, 1) + 1,
instr(str || ',', ',', 1, 2) - instr(str || ',', ',', 1, 1) - 1) AS cv
FROM t_str_row
UNION ALL
SELECT id,
3 AS p,
substr(str,
instr(str || ',', ',', 1, 1) + 1,
instr(str || ',', ',', 1, 2) - instr(str || ',', ',', 1, 1) - 1) AS cv
FROM t_str_row
ORDER BY 1, 2;
適用范圍：10g及以后版本
SELECT id, 1 AS p, rtrim(regexp_substr(str||',', '.*?' || ',', 1, 1), ',') AS cv
FROM t_str_row
UNION ALL
SELECT id, 2 AS p, rtrim(regexp_substr(str||',', '.*?' || ',', 1, 2), ',') AS cv
FROM t_str_row
UNION ALL
SELECT id, 3 AS p, rtrim(regexp_substr(str||',', '.*?' || ',',1,3), ',') AS cv
FROM t_str_row
ORDER BY 1, 2;
7.2
VARRAY
適用范圍：8i,9i,10g及以后版本
要創(chuàng)建一個可變數(shù)組：
CREATE OR REPLACE TYPE ins_seq_type IS VARRAY(8) OF NUMBER;
SELECT * FROM TABLE(ins_seq_type(1, 2, 3, 4, 5));
SELECT t.id,
c.column_value AS p,
substr(t.ca,
instr(t.ca, ',', 1, c.column_value) + 1,
instr(t.ca, ',', 1, c.column_value + 1) -
(instr(t.ca, ',', 1, c.column_value) + 1)) AS cv
FROM (SELECT id,
',' || str || ',' AS ca,
length(str || ',') - nvl(length(REPLACE(str, ',')), 0) AS cnt
FROM t_str_row) t
INNER JOIN TABLE(ins_seq_type(1, 2, 3)) c ON c.column_value <=
t.cnt
ORDER BY 1, 2;
7.3
SEQUENCE SERIES
這類方法主要是要產(chǎn)生一個連續(xù)的整數(shù)列，產(chǎn)生連續(xù)整數(shù)列的方法有很多，主要有：
CONNECT BY,ROWNUM+all_objects,CUBE等。
適用范圍：8i,9i,10g及以后版本
SELECT t.id,
c.lv AS p,
substr(t.ca,
instr(t.ca, ',', 1, c.lv) + 1,
instr(t.ca, ',', 1, c.lv + 1) -
(instr(t.ca, ',', 1, c.lv) + 1)) AS cv
FROM (SELECT id,
',' || str || ',' AS ca,
length(str || ',') - nvl(length(REPLACE(str, ',')), 0) AS cnt
FROM t_str_row) t,
(SELECT LEVEL lv FROM dual CONNECT BY LEVEL <= 5) c
WHERE c.lv <= t.cnt
ORDER BY 1, 2;
SELECT t.id,
c.rn AS p,
substr(t.ca,
instr(t.ca, ',', 1, c.rn) + 1,
instr(t.ca, ',', 1, c.rn + 1) -
(instr(t.ca, ',', 1, c.rn) + 1)) AS cv
FROM (SELECT id,
',' || str || ',' AS ca,
length(str || ',') - nvl(length(REPLACE(str, ',')), 0) AS cnt
FROM t_str_row) t,
(SELECT rownum rn FROM all_objects WHERE rownum <= 5) c
WHERE c.rn <= t.cnt
ORDER BY 1, 2;
SELECT t.id,
c.cb AS p,
substr(t.ca,
instr(t.ca, ',', 1, c.cb) + 1,
instr(t.ca, ',', 1, c.cb + 1) -
(instr(t.ca, ',', 1, c.cb) + 1)) AS cv
FROM (SELECT id,
',' || str || ',' AS ca,
length(str || ',') - nvl(length(REPLACE(str, ',')), 0) AS cnt
FROM t_str_row) t,
(SELECT rownum cb FROM (SELECT 1 FROM dual GROUP BY CUBE(1, 2))) c
WHERE c.cb <= t.cnt
ORDER BY 1, 2;
適用范圍：10g及以后版本
SELECT t.id,
c.lv AS p,
rtrim(regexp_substr(t.str || ',', '.*?' || ',', 1, c.lv), ',') AS cv
FROM (SELECT id,
str,
length(regexp_replace(str || ',', '[^' || ',' || ']', NULL)) AS cnt
FROM t_str_row) t
INNER JOIN (SELECT LEVEL lv FROM dual CONNECT BY LEVEL <= 5) c ON c.lv <= t.cnt
ORDER BY 1, 2;
7.4
HIERARCHICAL + DBMS_RANDOM
適用范圍：10g及以后版本
SELECT id,
LEVEL AS p,
rtrim(regexp_substr(str || ',', '.*?' || ',', 1, LEVEL), ',') AS cv
FROM t_str_row
CONNECT BY id = PRIOR id
AND PRIOR dbms_random.VALUE IS NOT NULL
AND LEVEL <=
length(regexp_replace(str || ',', '[^' || ',' || ']', NULL))
ORDER BY 1, 2;
7.5
HIERARCHICAL + CONNECT_BY_ROOT
適用范圍：10g及以后版本
SELECT id,
LEVEL AS p,
rtrim(regexp_substr(str || ',', '.*?' || ',', 1, LEVEL), ',') AS cv
FROM t_str_row
CONNECT BY id = connect_by_root id
AND LEVEL <=
length(regexp_replace(str || ',', '[^' || ',' || ']', NULL))
ORDER BY 1, 2;
7.6
MODEL
適用范圍：10g及以后版本
SELECT id, p, cv FROM t_str_row
MODEL
RETURN UPDATED ROWS
PARTITION BY(ID)
DIMENSION BY( 0 AS p)
MEASURES( str||',' AS cv)
RULES UPSERT
(cv
[ FOR p
FROM 1 TO length(regexp_replace(cv[0],'[^'||','||']',null))
例子：
SELECT t.dutyname , substr(sys_connect_by_path(t.username, ','), 2) str
FROM (SELECT dutyname, username, row_number() over(PARTITION BY dutyname ORDER BY username) rn
FROM test) t
WHERE connect_by_isleaf = 1
START WITH rn = 1
CONNECT BY rn = PRIOR rn + 1
AND dutyname = PRIOR dutyname;