|
Note: Decode and Case are very similar in their appearance but can produce very different results. |
| Demo Tables & Data |
|
| DECODE (overload 1) |
standard.decode(expr NUMBER, pat NUMBER, res NUMBER) RETURN NUMBER; |
| DECODE (overload 2) |
standard.decode(
expr NUMBER,
pat NUMBER,
res VARCHAR2 CHARACTER SET ANY_CS)
return VARCHAR2 CHARACTER SET res%CHARSET; |
| DECODE (overload 3) |
standard.decode(expr NUMBER, pat NUMBER, res DATE) RETURN DATE; |
| DECODE (overload 4) |
standard.decode(
expr VARCHAR2 CHARACTER SET ANY_CS,
pat VARCHAR2 CHARACTER SET expr%CHARSET,
res NUMBER)
RETURN NUMBER; |
| DECODE (overload 5) |
standard.decode(
expr VARCHAR2 CHARACTER SET ANY_CS,
pat VARCHAR2 CHARACTER SET expr%CHARSET,
res VARCHAR2 CHARACTER SET ANY_CS)
RETURN VARCHAR2 CHARACTER SET res%CHARSET; |
| DECODE (overload 6) |
standard.decode(
expr VARCHAR2 CHARACTER SET ANY_CS,
pat VARCHAR2 CHARACTER SET expr%CHARSET,
res DATE)
RETURN DATE; |
| DECODE (overload 7) |
standard.decode(expr DATE, pat DATE, res NUMBER) RETURN NUMBER; |
| DECODE (overload 8) |
standard.decode(
expr DATE,
pat DATE,
res VARCHAR2 CHARACTER SET ANY_CS)
RETURN VARCHAR2 CHARACTER SET res%CHARSET; |
| DECODE (overload 9) |
standard.decode(
expr DATE,
pat DATE,
res DATE) RETURN DATE; |
| DECODE (overload 10) |
standard.decode(expr OBJECT, pat
OBJECT, res OBJECT) RETURN OBJECT; |
| DECODE (overload 11) |
standard.decode(expr UNDEFINED,
pat UNDEFINED, res UNDEFINED)
RETURN UNDEFINED; |
| |
| Decode Built-in Function |
Simple DECODE |
SELECT DECODE (value, <if this value>, <return this value>)
FROM dual; |
SELECT program_id,
DECODE(customer_id, 'AAL', 'American Airlines') AIRLINE,
delivered_date
FROM airplanes
WHERE ROWNUM < 11; |
More Complex DECODE |
SELECT DECODE (value,<if this value>,<return this value>,
<
if this value>,<return this value>,
....)
FROM dual; |
SELECT program_id,
DECODE(customer_id,
'AAL', 'American Airlines',
'ILC', 'Intl. Leasing Corp.',
'NWO', 'Northwest Orient',
'SAL', 'Southwest Airlines',
'SWA', 'Sweptwing Airlines',
'USAF', 'U.S. Air Force') AIRLINE,
delivered_date
FROM airplanes
WHERE ROWNUM < 11; |
DECODE with DEFAULT |
SELECT DECODE (value,<if this value>,<return this value>,
<if this value>,<return this value>,
....
<otherwise this value>)
FROM dual; |
SELECT program_id,
DECODE(customer_id,
'AAL', 'American Airlines',
'ILC', 'Intl. Leasing Corp.',
'NWO', 'Northwest Orient',
'SAL', 'Southwest Airlines',
'SWA',
'Sweptwing Airlines',
'USAF', 'United States
Air Force',
'Not Known') AIRLINE,
delivered_date
FROM airplanes
WHERE ROWNUM < 11; |
| Note: The
following crosstabulation is the standard for 10g or earlier. In 11g use
the PIVOT and UNPIVOT operators |
Simple DECODE Crosstab
Note how each decode only looks at a single possible value and turns it into a new column |
SELECT program_id,
DECODE(customer_id,
'AAL', 'AAL') AMERICAN,
DECODE(customer_id,
'DAL', 'DAL') DELTA,
DECODE(customer_id,
'NWO', 'NWO') NORTHWEST,
DECODE(customer_id,
'ILC', 'ILC') INTL_LEASING
FROM airplanes
WHERE rownum < 20; |
DECODE as an in-line view with crosstab summation |
The above DECODE, in blue,
used as an in-line view |
SELECT program_id,
COUNT (AMERICAN) AAL,
COUNT (DELTA) DAL,
COUNT (NORTHWEST) NWO,
COUNT(INTL_LEASING) ILC
FROM (
SELECT program_id,
DECODE(customer_id, 'AAL', 'AAL') AMERICAN,
DECODE(customer_id, 'DAL', 'DAL') DELTA,
DECODE(customer_id, 'NWO', 'NWO') NORTHWEST,
DECODE(customer_id, 'ILC', 'ILC') INTL_LEASING
FROM airplanes)
GROUP BY program_id; |
Query for DECODE demo |
CREATE TABLE stores (
store_name VARCHAR2(20),
region_dir NUMBER(5),
region_mgr NUMBER(5),
store_mgr1 NUMBER(5),
store_mgr2 NUMBER(5),
asst_storemgr1 NUMBER(5),
asst_storemgr2 NUMBER(5),
asst_storemgr3 NUMBER(5));
INSERT INTO stores
VALUES ('San Francisco',100,200,301,302,401,0,403);
INSERT INTO stores
VALUES ('Oakland',100,200,301,0,404,0,0);
INSERT INTO stores
VALUES ('Palo Alto',100,200,0,305,0,405,406);
INSERT INTO stores
VALUES ('Santa Clara',100,250,0,306,0,0,407);
COMMIT;
SELECT DECODE(asst_storemgr1, 0,
DECODE(asst_storemgr2, 0,
DECODE(asst_storemgr3, 0, 0, asst_storemgr3),
asst_storemgr2), asst_storemgr1)
ASST_MANAGER,
DECODE(store_mgr1,0, DECODE(store_mgr2,0, 0, store_mgr2),
store_mgr1) STORE_MANAGER,
REGION_MGR,
REGION_DIR
FROM stores; |
DECODE with Summary Function |
SELECT SUM(CA_COUNT) CA,
SUM(TX_COUNT) TX
FROM (
SELECT state,
DECODE(state, 'CA', COUNT(*), 0) CA_COUNT,
DECODE(state, 'TX', COUNT(*), 0) TX_COUNT
FROM locations
GROUP BY state); |
DECODE in the WHERE clause |
set serveroutput on
DECLARE
posn PLS_INTEGER := 0;
empid PLS_INTEGER := 178;
x NUMBER;
BEGIN
SELECT NVL(SUM(ah.quantity * ah.saleprice * ap.payoutpct), 0)
INTO x
FROM accessoryhistory ah, payoutpercentage ap,
sku s, store st
WHERE empid = DECODE(posn,
0, st.areadir,
1, st.areamgr,
2, NVL(st.storemgr1, st.storemgr2),
3, NVL(st.asstmgr1, NVL(st.asstmgr2,
st.asstmgr3)))
AND ah.statustype IN ('ACT', 'DEA')
AND ah.store = st.store
AND s.dbid = ah.dbid
AND s.sku = ah.sku
AND ap.productgroup = s.productgroup
AND ap.position = posn;
dbms_output.put_line(x);
END;
/ |
DECODE Altered WHERE Clause
Thanks to HJL |
CREATE TABLE test (
pubdate DATE,
compdate DATE,
valuecol NUMBER(5));
INSERT INTO test VALUES (TRUNC(SYSDATE), TRUNC(SYSDATE+300), 1);
INSERT INTO test VALUES (TRUNC(SYSDATE-300), TRUNC(SYSDATE), 9);
COMMIT;
SELECT * FROM test;
CREATE OR REPLACE PROCEDURE testproc (
StartDate DATE, EndDate DATE, DateType IN VARCHAR2) IS
i PLS_INTEGER;
BEGIN
SELECT valuecol
INTO i
FROM test
WHERE DECODE(DateType, 'AA',compdate, 'BB', pubdate, compdate) <= EndDate
AND DECODE(DateType, 'AA', compdate, 'BB', pubdate, compdate) >= StartDate;
dbms_output.put_line(TO_CHAR(i));
END testproc;
/
set serveroutput on
exec testproc(TRUNC(SYSDATE), TRUNC(SYSDATE), 'BB'); |
| |
| CASE |
Simple CASE Demo |
SELECT CASE WHEN (<column_value>= <value>) THEN
WHEN (<column_value> =
<value>) THEN
ELSE <value>
FROM <table_name>; |
SELECT line_number,
CASE WHEN (line_number = 1) THEN
'One'
WHEN (line_number = 2) THEN
'Two'
ELSE 'More Than Two'
END AS RESULTSET
FROM airplanes; |
More Complex CASE Demo With Between |
SELECT CASE WHEN (<column_value>
BETWEEN <value>
AND <value>) THEN
WHEN (<column_value>
BETWEEN <value> AND <value>) THEN
ELSE <value>
FROM <table_name>; |
SELECT line_number,
CASE WHEN (line_number BETWEEN 1 AND 10) THEN 'One'
WHEN (line_number BETWEEN 11 AND 100) THEN 'Big'
ELSE 'Bigger'
END
FROM airplanes; |
More Complex CASE Demo With
Booleans |
SELECT CASE WHEN (<column_value> <= <value>) THEN
WHEN (<column_value>
<= <value>) THEN
ELSE <value>
FROM <table_name>; |
SELECT line_number,
CASE WHEN (line_number < 10) THEN 'Ones'
WHEN (line_number < 100) THEN 'Tens'
WHEN (line_number < 1000) THEN 'Hundreds'
ELSE 'Thousands'
END RESULT_SET
FROM airplanes; |
The above demo turned into a view |
CREATE OR REPLACE VIEW line_number_view AS
SELECT line_number,
CASE WHEN (line_number < 10) THEN 'Ones'
WHEN (line_number < 100) THEN 'Tens'
WHEN (line_number < 1000) THEN 'Hundreds'
ELSE 'Thousands'
END RESULT_SET
FROM airplanes; |
CASE with BOOLEANS |
set serveroutput on
DECLARE
boolvar BOOLEAN := TRUE;
BEGIN
dbms_output.put_line(CASE boolvar WHEN TRUE THEN 'TRUE' WHEN FALSE THEN
'FALSE' END);
END;
/ |
| |
| CASE - DECODE Comparison |
The same functionality written using both functions |
SELECT parameter,
DECODE(SIGN(parameter-1000),-1,'C','P') AS BAND
FROM parameter_table;
SELECT parameter,
CASE WHEN parameter < 1000 THEN 'C' ELSE 'P' END AS BAND
FROM parameter_table; |
Another example using SIGN |
SELECT min_cached, COUNT(*), ROUND(AVG(executions),2)
FROM (
SELECT DECODE(min_cached,
0, '1) 00-01 min',
1, '2) 01-02min',
2, '2) 01-02min',
DECODE(SIGN(min_cached -6), -1, '3) 03-05min',
DECODE(SIGN(min_cached -16), -1, '4) 06-15min',
DECODE(SIGN(min_cached -31), -1, '5) 16-30min',
DECODE(SIGN(min_cached -61), -1, '6) 31-60min',
DECODE(SIGN(min_cached-121), -1, '7) 1-2hrs',
'8) 2 hrs+ ')))))) min_cached,
executions
FROM (
SELECT ROUND((SYSDATE -
TO_DATE(first_load_time,'YYYY-MM-DD/HH24:MI:SS'))*24*60) min_cached,
executions
FROM gv$sqlarea
WHERE parsing_user_id != 0)
)
GROUP BY min_cached |
|
