SQL Workshop - Washington University in St. Louis
[Pages:62]SQL Workshop
Data Types
Doug Shook
Data Types
Four categories ? String ? Numeric ? Temporal ? Other
26 types total
2
Numeric Types
The integer data types
Type bigint int smallint tinyint bit
Bytes 8 4 2 1 1
The decimal data types
Type decimal[(p[,s])] numeric[(p[,s])] money 8 smallmoney
Bytes 5-17 5-17
4
The real data types
Type float[(n)] real
Bytes 4 or 8 4
3
Numeric Types
Decimal data types include precision and scale ? Precision: total number of digits ? Scale: number of digits to the right of decimal
Integer and decimal types are exact ? Real data types include a small amount of error
4
String Types
String data types for storing standard characters
Type char[(n)] varchar[(n)]
Bytes n
String data types for storing Unicode characters
Type nchar(n) nvarchar(n)
Bytes 2?n
5
Date/time Types
Date/time data types prior to SQL Server 2008
Type datetime
Bytes 8
smalldatetime
4
Date/time data types for SQL Server 2008 and later
Type date 3 time(n) 3-5 datetime2(n) datetimeoffset(n)
Bytes
6-8 8-10
6
Date/time Types
Common date formats
Format
yyyy-mm-dd mm/dd/yyyy mm-dd-yy Month dd, yyyy Mon dd, yy dd Mon yy
Example
2012-04-30 4/30/2012 4-30-12 April 30, 2012 Apr 30, 12 30 Apr 12
Common time formats
Format
hh:mi 16:20 hh:mi am/pm hh:mi:ss hh:mi:ss:mmm hh:mi:ss.nnnnnnn
Example
4:20 pm 4:20:36 4:20:36:12 4:20:36.1234567
7
Date/time Types
Dates and times can be coded as literals ? Surround with single quotes (`')
If a time is not specified with a date, it defaults to 12AM
If a date is not specified with a time, it defaults to 1/1/1900
The two-digit year cutoff is 50 ? 12 is 2012 ? 75 is 1975
8
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