Department of Computer and Information Science,
School of Science, IUPUI
Queries
Dale Roberts, Lecturer
Computer Science, IUPUI
E-mail: [email protected]
Dale Roberts
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Getting Text Information and Changing It
There are 2 kinds of functions. Functions either:
return modified the data.
return information about the data.
There are many kinds of functions:
String functions (Chapter 7)
Numeric functions (Chapter 8)
Date functions (Chapter 9)
Conversion functions (Chapter 10)
Group functions (Chapter 11)
DECODE and CASE (Chapter 17)
User Defined (Chapter 29)
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String Functions
CHAR and VARCHAR2 are “string” data types in Oracle.
CHAR is fixed length, VARCHAR2 is variable length.
|| is for string concatenation. For example:
SELECT CITY||’, ’||STATE||’
FROM CUSTOMER;
•
•
•
•
’||ZIP AS ADDRESS
ADDRESS
-----------------------------------------INDIANAPOLIS, IN 46250
RED WOOD SHORES, ca 94710
INITCAP, UPPER, LOWER changes capitalization. For example:
SELECT INITCAP(CITY)||’, ’||UPPER(STATE)||’
AS ADDRESS
FROM CUSTOMER;
•
•
•
’||ZIP
ADDRESS
-----------------------------------------Indianapolis, IN 46250
Red Wood Shores, CA 94710
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String Functions
SUBSTR returns only a part of a string. Example:
SELECT SUBSTR(ADDRESS,1,8)
FROM CUSTOMER;
•
SUBSTR(A
-------INDIANAP
RED WOOD
INSTR returns the relative position of a character within the string. Example:
SELECT ADDRESS, INSTR(ADDRESS, ’, ’)
FROM CUSTOMER;
•
•
•
•
ADDRESS
---------------------------INDIANAPOLIS, IN 46250
RED WOOD SHORES, CA 94710
INSTR(ADDRESS, ’, ’ )
--------------------13
16
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String Functions
Example combining INITCAP, SUBSTR and INSTR:
SELECT INITCAP(SUBSTR(ADDRESS,1,INSTR(ADDRESS,’, ’)-1))
FROM CUSTOMER;
INITCAP(SUBSTR(ADDRESS,1,INSTR(ADDRESS,’, ’)-1))
•
-----------------------------------------------•
Indianapolis
•
Red Wood Shores
LENGTH returns length of string.
LTRIM, RTRIM returns the string without the specified leading (ltrim) or
trailing (rtrim) characters. Excellent for cleaning up data fields that contain
garbage.
LPAD, RPAD returns the string with extra characters to pad out to the
specified length either on the left (lpad) or the right (rpad).
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Numeric Functions
Single Value Functions:
ABS, ACOS, ASIN, ATAN, ATAN2, BITAND, CEIL, COS, COSH, EXP, FLOOR,
LN, LOG, MOD, NVL, POWER, ROUND, SIGN, SIN, SINH, SQRT, TAN, TANH,
TRUNC, VSIZE Group Functions:
AVG, CORR, COUNT, COVAR_POP, COVAR_SAMP, CUME_DIST,
DENSE_RANK, FIRST, GROUP_ID, GROUPING, GROUPING_ID, LAST, MAX,
MIN, PERCENTILE_COUNT, PERCENTILE_DISC, PERCENT_RANK, RANK,
STDDEV, STDDEV_POP, STDDEV_SAMP, SUM, VAR_POP, VAR_SAMP,
VARIANCE List Functions:
COALESCE, GREATEST, LEAST Ø
9i new functions in bold italics
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Date Functions
Current date functions:
SYSDATE,
CURRENT_DATE,
CURRENT_TIMESTAMP, LOCALTIMESTAMP,
SESSIONTIMEZONE, SYSTIMESTAMP
Date functions:
ADD_MONTS, GREATEST, LEAST, LAST_DAY,
MONTHS_BETWEEN, NEW_TIME, NEXT_DAY,
TO_DATE, TO_CHAR, ROUND, TRUNC,
DBTIMEZONE, EXTRACT, FROM_TZ,
NUMTODSINTERVAL, NUMTOYMINTERVAL,
SYS_EXTRACT_UTC, TO_DSINTERVAL, TO_TIMESTAMP,
TO_TIMESTAMP_TZ, TO_YMINTERVAL, TZ_OFFSET Ø
9i new functions in bold italics
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Grouping Things Together
ANSI standard SQL Group functions:
AVG, COUNT, MAX, MIN, STDDEV, SUM, VARIANCE
Others:
8i: GROUPING (used with CUBE and ROLLUP, see Ch.13)
9i statistical functions: CORR, COVAR_POP, COVAR_SAMP, CUME_DIST,
DENSE_RANK, FIRST, FIRST_VALUE, GROUP_ID, GROUPING_ID,
LAST, PERCENTILE_CONT, PERCENTILE_DISC, PERCENT_RANK,
RANK, REGR, STDDEV_POP, STDDEV_SAMP, VAR_POP, VAR_SAMP
Obsolete? In 9i: GLB, LUB
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Grouping Things Together
A group function returns a single row for an entire group of
queried rows.
NULL values are ignored in group functions.
Without a GROUP BY clause the data returned for a group
function is one row for the entire table.
With a GROUP BY clause, one row is returned for each group your
data is subdivided into.
The WHERE clause is evaluated before data are grouped in
GROUP BY clause.
The HAVING clause is similar to the WHERE clause, but it works
on entire groups of data.
DISTINCT keyword forces only unique occurrences to be
considered in data groups.
When using a group by clause, these are the only selectable
items:
constants,
group functions, and
group expressions -- these must match exactly the group by clause
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Grouping Things Together
Order of clause execution within select statements:
1. If the statement contains a WHERE clause, removes all rows that do not
satisfy it.
2. Group rows together based on the GROUP BY clause.
3. Calculate the results of the group functions for each group.
4. Choose and eliminate groups based on the HAVING clause.
5. Order the results based on the ORDER BY clause.
Specify the GROUP BY and HAVING clauses after the WHERE clause. If
both the GROUP BY and HAVING clauses are specified, they can appear in
either order.
A side effect of GROUP BY is a ordered result, same effect as having an
ORDER BY clause of the GROUP BY columns.
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Grouping Things Together
Views over groups, commonly used for percent of total calculations.
Inline view example from p. 214:
select categoryname, counter,
(counter/bookcount)*100 “pct”
from category_count,
(select count(*) as bookcount from bookshelf)
order by categoryname;
Group expressions can be used in the HAVING clause, even those not
used in the SELECT clause.
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Acknowledgements
Loney, Oracle Database 10g The Complete Reference
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