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simplified data type table
amlaenxc Apr 2, 2025
a5ce09a
improve descriptions in epsiode 1 data types table, added data type q…
amlaenxc Apr 2, 2025
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50 changes: 10 additions & 40 deletions episodes/00-sql-introduction.md
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Expand Up @@ -235,46 +235,16 @@ You can also use this same approach to append new fields to an existing table.

### Data types {#datatypes}

| Data type | Description |
| ----------------------------------------------------- | :------------------------------------------------------------------------------------------------------- |
| CHARACTER(n) | Character string. Fixed-length n |
| VARCHAR(n) or CHARACTER VARYING(n) | Character string. Variable length. Maximum length n |
| BINARY(n) | Binary string. Fixed-length n |
| BOOLEAN | Stores TRUE or FALSE values |
| VARBINARY(n) or BINARY VARYING(n) | Binary string. Variable length. Maximum length n |
| INTEGER(p) | Integer numerical (no decimal). |
| SMALLINT | Integer numerical (no decimal). |
| INTEGER | Integer numerical (no decimal). |
| BIGINT | Integer numerical (no decimal). |
| DECIMAL(p,s) | Exact numerical, precision p, scale s. |
| NUMERIC(p,s) | Exact numerical, precision p, scale s. (Same as DECIMAL) |
| FLOAT(p) | Approximate numerical, mantissa precision p. A floating number in base 10 exponential notation. |
| REAL | Approximate numerical |
| FLOAT | Approximate numerical |
| DOUBLE PRECISION | Approximate numerical |
| DATE | Stores year, month, and day values |
| TIME | Stores hour, minute, and second values |
| TIMESTAMP | Stores year, month, day, hour, minute, and second values |
| INTERVAL | Composed of a number of integer fields, representing a period of time, depending on the type of interval |
| ARRAY | A set-length and ordered collection of elements |
| MULTISET | A variable-length and unordered collection of elements |
| XML | Stores XML data |

### SQL Data Type Quick Reference {#datatypediffs}
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I agree that the quick reference table is a lot for the lesson but would like to retain this in learners/sql-cheat-sheet.md.

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I've moved that quick reference table to learners/sql-cheat-sheet.md, and added a column for SQLite since that is the main database platform used in this workshop.


Different databases offer different choices for the data type definition.

The following table shows some of the common names of data types between the various database platforms:

| Data type | Access | SQLServer | Oracle | MySQL | PostgreSQL |
| :---------------------------------------------------- | :------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------- | :--------------- | :------------ | :------------ |
| boolean | Yes/No | Bit | Byte | N/A | Boolean |
| integer | Number (integer) | Int | Number | Int / Integer | Int / Integer |
| float | Number (single) | Float / Real | Number | Float | Numeric |
| currency | Currency | Money | N/A | N/A | Money |
| string (fixed) | N/A | Char | Char | Char | Char |
| string (variable) | Text (\<256) / Memo (65k+) | Varchar | Varchar2 | Varchar | Varchar |
| binary object OLE Object Memo Binary (fixed up to 8K) | Varbinary (\<8K) | Image (\<2GB) Long | Raw Blob | Text Binary | Varbinary |
SQLite has four data types, shown in the table below.

| Data type | Description |
| ----------------------------------------------------- | :----------------------------------------------------------------------------------------------------------------------------------------- |
| TEXT | Text string |
| INTEGER | Integer numerical (signed positive or negative) |
| REAL | Approximate numerical |
| BLOB | Multipurpose datatype with limited functionality that is generally used for data which does not fit into any of the other three categories |

In addition to these four data types, SQLite has a NULL value for missing data. We will talk more about dealing with missing data in Episode 3.

:::::::::::::::::::::::::::::::::::::::: keypoints

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16 changes: 16 additions & 0 deletions learners/sql-cheat-sheet.md
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Expand Up @@ -41,6 +41,22 @@ Sort results using `ASC` for ascending order or `DESC` for descending order:

SELECT * FROM table_name ORDER BY column_name_1 ASC, column_name_2 DESC;

Data Types
----------

Different databases offer different choices for the data type definition.

The following table shows some of the common names of data types between the various database platforms:

| Data type | Access | SQLServer | Oracle | MySQL | PostgreSQL | SQLite |
| :---------------------------------------------------- | :------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------- | :--------------- | :------------ | :------------ | :------ |
| boolean | Yes/No | Bit | Byte | N/A | Boolean | Integer |
| integer | Number (integer) | Int | Number | Int / Integer | Int / Integer | Integer |
| float | Number (single) | Float / Real | Number | Float | Numeric | Real |
| currency | Currency | Money | N/A | N/A | Money | Real |
| string (fixed) | N/A | Char | Char | Char | Char | Text |
| string (variable) | Text (\<256) / Memo (65k+) | Varchar | Varchar2 | Varchar | Varchar | Text |
| binary object OLE Object Memo Binary (fixed up to 8K) | Varbinary (\<8K) | Image (\<2GB) Long | Raw Blob | Text Binary | Varbinary | Blob |

Missing Data
------------
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