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31 lines
935 B
Markdown
31 lines
935 B
Markdown
# CIS105: Computer Applications & Information Systems Lect. 17
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## Chapter 17: SQL Clauses: `JOIN` Query
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### 17.1: `JOIN` & `ON` Clauses
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- `JOIN`: Join tables together to connect multiple fields into 1 query.
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- `ON`: Linking the primary and foreign key
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- Linking formula: `FROM table1 + JOIN table2 ON table1.primarykey = table2.foreignkey`
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```sql
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SELECT first_name, last_name, link_to_major, major_id, major_name
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FROM member
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JOIN major
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ON member. link_to_major = major.major_id
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```
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### 17.2: SQL Statements: Primary vs. Foreign Keys
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- Primary key: A field on a database table that uniquely identifies each row of the table.
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- Foreign key: is used to combine the rows from one table wit the rows of another table.
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### 17.3: SQL Statement: Date & Time Formatting
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- The common conventional format of SQL date & time searching is as followed, in form of `YEAR-MONTH-DATT12:00:00`
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- ```sql
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'2022-04-17T12:00:00'
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```
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