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Oracle Power Point
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5/28/2018 PPT DB25 Oracle 01Afternoon
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Basics of SQLOracle Day 1 Afternoon Session
5/28/2018 PPT DB25 Oracle 01Afternoon
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2Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
Objectives
To understand important SQL functions
To understand pseudo columns
5/28/2018 PPT DB25 Oracle 01Afternoon
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3Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
DUAL - The Dummy table
Automatically created table, which is part of the data dictionary
Contains one row and one column(varchar2(1): value = X)
Can be used to return constants once, with a SELECT statement
Belongs to SYS schema, accessible to all
eg: SELECT SYSDATE FROM DUAL
5/28/2018 PPT DB25 Oracle 01Afternoon
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4Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
SQL Functions - Decode
Decode
DECODE( expr , search , result [, search , result]... [, default] )
A DECODE function compares exprto each search value one by one. If expris
equal to a search, Oracle returns the corresponding result. If no match is found,
Oracle returns default, or, if defaultis omitted, returns null.
This example decodes the value warehouse_id. If warehouse_id is 1, the function
returns 'Southlake'; if warehouse_id is 2, it returns 'San Francisco'; etc. If
warehouse_id is not 1, 2, 3, or 4, the function returns 'Non-domestic'.
SELECT product_id, DECODE (warehouse_id, 1, 'Southlake', 2, 'San Francisco', 3,
'New Jersey', 4, 'Seattle', 'Non-domestic') quantity_on_hand FROM inventories;
5/28/2018 PPT DB25 Oracle 01Afternoon
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5Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
SQL Functions - Trim
Trim
TRIM enables you to trim leading or trailing characters (or both) from a character
string. If trim_characteror trim_sourceis a character literal, you must enclose it in
single quotes.
SELECT TRIM (0 FROM 0009872348900) "TRIM Example" FROM DUAL;
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6Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
SQL Functions - Substr
substr
The substring functions return a portion of string, beginning at characterposition,
substring_lengthcharacters long. SUBSTR calculates lengths using characters as
defined by the input character set. SUBSTRB uses bytes instead of characters.
SELECT SUBSTR('ABCDEFG',3,4) "Substring" FROM DUAL;
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7/147Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
SQL Functions - NVL
NVL
NVL( expr1 , expr2 )
If expr1is null, NVL returns expr2. If expr1is not null, NVL returns expr1.
The following example returns a list of employee names and commissions,
substituting "Not Applicable" if the employee receives no commission:
SELECT last_name, NVL(TO_CHAR(commission_pct), 'Not Applicable')
"COMMISSION" FROM employees WHERE last_name LIKE 'B%';
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8/148Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
SQL Functions - Translate
Translate
TRANSLATE( 'char' , 'from_string' , 'to_string' )
TRANSLATE returns charwith all occurrences of each character in from_string
replaced by its corresponding character in to_string. Characters in charthat are not
in from_stringare not replaced.
The following statement translates a license number. All letters 'ABC...Z' aretranslated to 'X' and all digits '012 . . . 9' are translated to '9':
SELECT TRANSLATE('2KRW229',
'0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ',
'9999999999XXXXXXXXXXXXXXXXXXXXXXXXXX') "License" FROM DUAL;
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9/149Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
SQL FunctionsTo_char
To_char
TO_CHAR( date , fmt )
TO_CHAR converts dateof DATE to a value of VARCHAR2 datatype in the format
specified by the date format fmt.
SELECT TO_CHAR(ts_col, 'DD-MON-YYYY HH24:MI:SS') FROM my_tab;
5/28/2018 PPT DB25 Oracle 01Afternoon
10/1410Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
Pseudocolumns
Behaves like a table column
Not stored in table Cannot change value of pseudocolumn
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11/1411Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
Pseudocolumns
CURRVAL
NEXTVAL
ROWID
ROWNUM
LEVEL(used for hierarchical queries)
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Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
Examples
SELECT empSeq.CURRVAL from DUAL;
SELECT ROWID, ENAME FROM EMP; SELECT ROWNUM, ENAME FROM EMP order by ename;
5/28/2018 PPT DB25 Oracle 01Afternoon
13/1413Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No. 2.0
Summary
To understand important SQL functions
To understand pseudo columns
5/28/2018 PPT DB25 Oracle 01Afternoon
14/1414Copyright 2005, Infosys
Technologies Ltd
ER/CORP/CRS/DB25/003
Version No 2 0
Thank You!