Basic SQL: Where, Order by,Comparision and Logical Conditions

http://superman-chenzs.itpub.net/post/29327/273849

SELECT *|{[DISTINCT] column|expression [alias],...}
FROM table
[WHERE condition(s)]
[ORDER BY Clause];


Limiting the Rows Selected
* Restrict rows returned by using the WHERE clause.


-----------------------------------------------------------------------------------------------------------------
Character Strings and Dates
- Character strings and date values are enclosed in single quotation marks
- Character values are case sensitive,and date values are format sensitive
- The default date formate is DD-MON-YY


------------------------------------------------------------------------------------------------------------------
Comparision Conditions
= : equla to
> : greater than
>= : greater than or equal to
< : less than
<= : less than or equal to
<> : not equal to

BETWEEN ... AND ... : between two values (inclusive)
IN (SET) : Match any of a list of values
LIKE : Match a character pattern
IS NULL: Is a null value
IS NOT NULL : Is not a null value


Using the LIKE Condition : Pattern-Matching
- Use the LIKE condition to perform wildcard searches of valid search string values
- Search conditions can contain either literal characters or numbers:
1. % denotes zero or many characters
2. _ denotes one characters
- You can combine pattern-matching characters
- You can use the ESCAPE identifier to search for the actual % and _ symbols


------------------------------------------------------------------------------------------------------------------
Logical Conditions
AND : Returns TRUE if both component conditions are true
OR : Returns TRUE if either component condition is true
NOT : Returns TRUE if the following condition is false (Before other keywords, eg: not like)


------------------------------------------------------------------------------------------------------------------
Rules of Precedence
1 -> Arithmetic operators
2 -> Concatenation operator
3 -> Comparison conditions
4 -> IS [NOT] NULL,[NOT] LIKE,[NOT] IN
5 -> [NOT] BETWEEN...AND...
6 -> NOT logical condition
7 -> AND logical condition
8 -> OR logical condition
Override rules of precedence by using parentheses


------------------------------------------------------------------------------------------------------------------
ORDER BY Clause
1.Sort rows with the ORDER BY clause
- ASC: ascending order,default
- DESC: descending order
2.The ORDER BY clause comes last in the SELECT statement
3.The order of ORDER BY list is the order of sort
4. You can sort by a column that is not in the SELECT list
5. You can sort by a column by using the alias name