Credit debit

In this example you are shown how to split a single column into two separate columns and also below you are

told how to combine two tables into a single table. Here we are splitting cash amounts into credit and debit.

Table 1 shows the results without the split column and Table 2 shows what we get when the column is split into two.

Table 1

whn	description	amount
2006-11-01	Wages	50
2006-11-02	Company Store	-10
2006-11-03	Company Store	-10
2006-11-04	Company Store	-10
2006-11-05	Company Store	-10
2006-11-06	Company Store	-10

Table 2

whn	description	cshIN	cshOUT
2006-11-01	Wages	50
2006-11-02	Company Store		10
2006-11-03	Company Store		10
2006-11-04	Company Store		10
2006-11-05	Company Store		10
2006-11-06	Company Store		10

schema:scott

DROP TABLE transact

 CREATE TABLE transact(
  whn DATE,
  description VARCHAR(20),
  amount INTEGER );
INSERT INTO transact VALUES ('2006-11-01','Wages',50);
INSERT INTO transact VALUES ('2006-11-02','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-03','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-04','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-05','Company Store',-10);
INSERT INTO transact VALUES ('2006-11-06','Company Store',-10);

To split a column into two you have to use a CASE function as shown in the example. The SUBSTRING used in the example is used to get rid of the negative sign infront of the number so that there are only positive numbers in the table.

To combine two columns into a single one you also use a CASE function to do this with this example you can use this code:

SELECT w AS dte, d AS description, 
   CASE WHEN (a>=0) 
   THEN a ELSE NULL END AS amount,
   CASE WHEN (b>=0) 
   THEN b ELSE NULL END AS amount
  FROM
  (SELECT x.whn AS w, x.description AS d, 
          x.cshIN AS a, x.cshOUT AS b
     FROM transact x
     JOIN transact y ON (x.whn>=y.whn)
     GROUP BY x.whn, x.description, x.amount) t

SELECT w AS dte, d AS description, 
   CASE WHEN (a>=0) THEN a ELSE NULL END AS cshIN,
   CASE WHEN (a<0) THEN SUBSTRING(a,2,10) ELSE NULL END AS cshOUT
  FROM
  (SELECT x.whn AS w, x.description AS d, 
          x.amount AS a
     FROM transact x
     JOIN transact y ON (x.whn>=y.whn)
     GROUP BY x.whn, x.description, x.amount) t

SELECT w AS dte, d AS description, 
   CASE WHEN (a>=0) THEN a ELSE NULL END AS cshIN,
   CASE WHEN (a<0) THEN SUBSTR(a,2,10) ELSE NULL END AS cshOUT
  FROM
  (SELECT x.whn AS w, x.description AS d, 
          x.amount AS a
     FROM transact x
     JOIN transact y ON (x.whn>=y.whn)
     GROUP BY x.whn, x.description, x.amount) t

SQL HACKS

Hack 10 Converting subqueries into joins

Hack 11 Converting aggregate subqueries into joins

Hack 14 Generate Combinations

Hack 16 Search for a String across columns

Hack 24 Multiply Across a Result Set

Hack 25 Keep a running total

Hack 25.5 Splitting and combining columns

Hack 26 Include the rows your JOIN forgot

Hack 30 Calculate the maximum/minimum of two fields

Hack 33 Get values and subtotals in one shot

Hack 50 Combine tables containing different data

Hack 51/52 Display rows as columns

Hack 55 Import Someone Else's Data

Hack 62 Issue Queries Without Using a Table

Hack 63 Generate rows without tables

Hack 70 Combine your queries

Hack 72 Extract a subset of the results

Hack 78 Break it down by Range

Hack 88 Test two values from a subquery

Hack 98 Find and stop long running queries

Hack 100 Run SQL from a Web Page