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simplified data type table #385

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simplified data type table
alexthrelkeld Apr 2, 2025
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improve descriptions in epsiode 1 data types table, added data type q…
alexthrelkeld Apr 2, 2025
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44 changes: 7 additions & 37 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}

SQLite has four data types, shown in the table below.

| 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. |
| TEXT | Character string |
| BLOB | Raw binary data |
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@adamancer adamancer Apr 2, 2025

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I would not count on learners knowing what binary data is. You might include examples (image file, etc.)

Is BLOB in SQLite always binary? That's generally what BLOB implies but the definition here suggests the BLOB format just stores the data as is.

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@alexthrelkeld alexthrelkeld Apr 2, 2025

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I'm not exactly sure what the documentation means for the BLOB datatype with regards to whether it is always stored as raw binary. In any case, I updated the description in the table to avoid referencing "binary data" and hopefully be more understandable.

| INTEGER | Integer numerical (signed positive or negative) |
| 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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@adamancer adamancer Apr 2, 2025

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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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@alexthrelkeld alexthrelkeld Apr 2, 2025

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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 |

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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