SQL Data Types
Submitted by admin on Monday, April 18, 2011 - 15:28.
The data type determines the kind of values that users can store in the field. Like every programming languages, the SQL also has specific data type to store data. Following are some data type and there descriptions in which SQL allows us to store data.
Microsoft Access Data Types
Source: Microsoft Access Help
| Setting | Type of data | Size |
|---|---|---|
| Text | (Default) Text or combinations of text and numbers, as well as numbers that don't require calculations, such as phone numbers. | Up to 255 characters or the length set by the FieldSize property, whichever is less. Microsoft Access does not reserve space for unused portions of a text field. |
| Memo | Lengthy text or combinations of text and numbers. | Up to 65,535 characters. (If the Memo field is manipulated through DAO and only text and numbers [not binary data] will be stored in it, then the size of the Memo field is limited by the size of the database.) |
| Number | Numeric data used in mathematical calculations. For more information on how to set the specific Number type, see the FieldSize property topic. | 1, 2, 4, or 8 bytes (16 bytes if the FieldSize property is set to Replication ID). |
| Date/Time | Date and time values for the years 100 through 9999. | 8 bytes. |
| Currency | Currency values and numeric data used in mathematical calculations involving data with one to four decimal places. Accurate to 15 digits on the left side of the decimal separator and to 4 digits on the right side. | 8 bytes. |
| AutoNumber | A unique sequential (incremented by 1) number or random number assigned by Microsoft Access whenever a new record is added to a table. AutoNumber fields can't be updated. For more information, see the NewValues property topic. | 4 bytes (16 bytes if the FieldSize property is set to Replication ID). |
| Yes/No | Yes and No values and fields that contain only one of two values (Yes/No, True/False, or On/Off). | 1 bit. |
| OLE Object | An object (such as a Microsoft Excel spreadsheet, a Microsoft Word document, graphics, sounds, or other binary data) linked to or embedded in a Microsoft Access table. | Up to 1 gigabyte (limited by available disk space) |
| Hyperlink | Text or combinations of text and numbers stored as text and used as a hyperlink address. A hyperlink address can have up to three parts:
text to display— the text that appears in a field or control. address— the path to a file (UNC path) or page (URL). subaddress— a location within the file or page. screentip— the text displayed as a tooltip. The easiest way to insert a hyperlink address in a field or control is to click Hyperlink on the Insert menu. |
Each part of the three parts of a Hyperlink data type can contain up to 2048 characters. |
| Lookup Wizard | Creates a field that allows you to choose a value from another table or from a list of values by using a list box or combo box. Clicking this option starts the Lookup Wizard, which creates a Lookup field. After you complete the wizard, Microsoft Access sets the data type based on the values selected in the wizard. | The same size as the primary key field used to perform the lookup, typically 4 bytes. |
SQL Server Data Types
| Datatype | Storage | Type |
|---|---|---|
| Bigint | 8 bytes | Exact numeric |
| Int | 4 bytes | Exact numeric |
| Smallint | 2 bytes | Exact numeric |
| Tinyint | 1 bytes | Exact numeric |
| Bit | 1 to 8 bit columns in the same table requires a total of 1 byte, 9 to 16 bits = 2 bytes, etc... | Exact numeric |
| Decimal | Precision 1-9 = 5 bytes, precision 10-19 = 9 bytes, precision 20-28 = 13 bytes, precision 29-38 = 17 bytes |
Exact numeric |
| Numeric | ||
| Money | 8 bytes | Exact numeric |
| Smallmoney | 4 bytes | Exact numeric |
| Float | 4 bytes when precision is less than 25 and 8 bytes when precision is 25 through 53 | Approximate numerics |
| Real | 4 bytes | Approximate numerics |
| Datetime | 8 bytes | Date and time |
| Smalldatetime |
Date and time | |
| Date | Date and time | |
| Time | Date and time | |
| Datetime2 | Presicion 1-2 = 6 bytes precision 3-4 = 7 bytes precision 5-7 = 8 bytes | Date and time |
| Datetimeoffset | Presicion 1-2 = 8 bytes precision 3-4 = 9 bytes precision 5-7 = 10 bytes | Date and time |
| Char | Defined width | Character string |
| Varchar | 2 bytes + number of chars | Character string |
| Varchar(max) | 2 bytes + number of chars | Character string |
| Text | 4 bytes + number of chars | Character string |
| Nchar | Defined width x 2 | Unicode character string |
| Nvarchar | Unicode character string | |
| Nvarchar(max) | Unicode character string | |
| Ntext | Unicode character string | |
| Binary | Binary string | |
| Varbinary | Binary string | |
| Varbinary(max) | Binary string | |
| Image | Binary string | |
| Sql_variant | Other | |
| Timestamp | Other | |
| Uniqueidentifier | Other | |
| Xml | Other | |
| Cursor | Other | |
| Table | Other |
MySQL Data Types
| Type | Size | Description |
|---|---|---|
| CHAR[Length] | Length bytes | A fixed-length field from 0 to 255 characters long. |
| VARCHAR(Length) | String length + 1 bytes | A fixed-length field from 0 to 255 characters long. |
| TINYTEXT | String length + 1 bytes | A string with a maximum length of 255 characters |
| TEXT | String length + 2 bytes | A string with a maximum length of 65,535 characters. |
| MEDIUMTEXT | String length + 3 bytes | A string with a maximum length of 16,777,215 characters. |
| LONGTEXT | String length + 4 bytes | A string with a maximum length of 4,294,967,295 characters. |
| TINYINT[Length] | 1 byte | Range of -128 to 127 or 0 to 255 unsigned. |
| SMALLINT[Length] | 2 bytes | Range of -32,768 to 32,767 or 0 to 65,535 unsigned. |
| MEDIUMINT[Length] | 3 bytes | Range of -8,388,608 to 8,388,607 or 0 to 16,777,215 unsigned |
| INT[Length] | 4 bytes | Range of -2,147,483,648 to 2,147,483,647 or 0 to 4,294,967,295 unsigned |
| BIGINT[Length] | 8 bytes | Range of -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 or 0 to 18,446,744,073,709,551,615 unsigned |
| FLOAT | 4 bytes | A small number with a floating decimal point. |
| DOUBLE[Length, Decimals] | 8 bytes | A large number with a floating decimal point. |
| DECIMAL[Length, Decimals] | Length +1 bytes or Length + 2 bytes |
A DOUBLE stored as a string, allowing for a fixed decimal point. |
| DATE | 3 bytes | In the format YYYY-MM-DD |
| DATETIME | 8 bytes | In the format YYYY-MM-DD HH:MM:SS. |
| TIMESTAMP | 4 bytes | In the format YYYYMMDDHHMMSS; acceptable range ends in the year 2037. |
| TIME | 3 bytes | In the format of HH:MM:SS. |
Every DBMS has its own set of rules on the data type. Some are not SQL standards. The above list are simply a representation of most common term use to describe the meaning of every data type.
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