doc(cis105): add lecture note for lecture 14 on sql statements & add its affiliated sidebar hyperlink components for quick accesses

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Anda Toshiki 2024-04-04 10:47:38 -07:00
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@ -225,6 +225,10 @@ export const sidebar: DefaultTheme.Config['sidebar'] = {
{ {
text: 'Lect 13: Information Systems in Business', text: 'Lect 13: Information Systems in Business',
link: '/academic/cis105/cis105-l13-lecture-note', link: '/academic/cis105/cis105-l13-lecture-note',
},
{
text: 'Lect 14: More SQL Statements',
link: '/academic/cis105/cis105-l14-lecture-note'
} }
], ],
}, },

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# CIS105: Computer Applications & Information Systems Lect. 14
## Chapter 14: More SQL Statement
### 14.1: Statement Review
- `SELECT`: What **fields** (column) you want
- `fieldname`: If the name is used in only one table
- `FROM`: What table or tables contain the fields
- `ORDER BY`: Sorting
- `DISTINCT`: Use after `SELECT` when you only want to show each vale of the selected field(s) once
- `LIMIT`: Use when you want to limit the number of records produced
### 14.2: New SQL Statements
- `WHERE`: Applies conditions, filters
- `WHERE` clause conditions follow a pattern: field + comparison operator + value
- ```sql
WHERE crime.iucr_no = 420
```
- Comparison Operators:
- `>` : Returns all records larger than the specified value
- `>=`: Returns all records that are at least as large as the specified value (including the value)
- `<` : Returns all records smaller than the specified value
- `<=`: Returns all records that are at least as small as the specified value (including the value)
- `=` : Returns all records that are exactly equal to the specified value
- `<>`: Returns all records that are not equal to the specified value
- `NULL`: An empty value
- `NOT`: Can be used to create a condition that reverses the logic of any condition
- Similar logic to the `NOT` function in Excel
- `AND`: Both conditions must be met for row to be included in query
- `OR`: Used to combine criteria when we want our results to mach any criteria
- `BETWEEN`: Shorthand way to include values in a range
- `IN`: Shorthand way to include values in a range
- `LIKE`: Use this statement when you aren't sure of the values in a record
- `%`: any combination of characters
- `%Keyword`: ends with keyword
- `%Keyword%`: looks for %keyword% anywhere in the record
- `Keyword%`: starts with keyword
- `-` substitutes for any single character
- '`t_p`' would return '`tip`', '`tap`', or '`top`''; but not '`stop`'
- '`p_st`" would return '`past`"', but not '`paste`'
- `'h__s_n'` would return '`hanson`', 'hensen', or 'hansen'; but not 'harrison' (note that
'h%s_n' would return 'harrison'
### 14.3: Rules to Remember
- To combine `AND` and `OR` statements, you must follow the order of operations (`AND` 1st, `OR` 2nd)
- If `OR` must be first, use `()`
- All words must be in between `('_')`, `("_")`
- If your value contains a quotation, use double quotation or a `/`
- All `#s` is left as-is