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SQL_Fun

From the LinkedIn Learning Course "SQL Essential Training"

Objective: Learn a new SQL tool (SQLiteStudio) and further familiarize myself with essential SQLite functions.

Skills Covered:

  • How DataBases are organized
  • Selecting rows and columns
  • Creating new tables
  • Inserting and updating data
  • Sorting and filtering
  • Accessing related tables with JOIN
  • Working with strings
  • Understanding numeric types
  • Using aggregate functions and transactions
  • Automating data with triggers
  • Creating views
  • Using CRUD functions

Fundamental Concepts:

  • CREATE TABLE
  • INSERT INTO
  • DROP TABLE / DROP TABLE IF EXISTS
  • ID
  • NULL
  • SELECT
  • DELETE
  • Constraints: UNIQUE
  • ALTER TABLE
  • WHERE, LIKE, IN
  • SELECT DISTINCT
  • ORDER BY
  • CASE WHEN

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String Functions:

  • SINGLE QUOTES
  • CONCATENATION

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  • LENGTH

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  • SUBSTR

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  • TRIM

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  • UPPER/LOWER

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Numeric Types:

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DATE/TIME:

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Aggregations:

  • HAVING clause opperates on aggregated data
  • WHERE is used before a GROUP BY, HAVING is used after GROUP BY and before ORDER BY
  • AGGREGATE functions include but are not limited to: COUNT, AVG, MIN, MAX, SUM.

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Transactions:

  • Transactions are a group of operations that are handled as one unit of work. They improve performance.
  • Transactions can add information to one table and remove the same information from another table at the same time.

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  • ROLLBACK is used to undo a transaction before it is completed in the event of an error.

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  • This insert statement adding 1000 lines to a table required 2.024 seconds to run without transaction. With transaction it required 0.036 seconds.

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Triggers

  • Triggers are operations that are automatically performed when a specified database event occurs.

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  • Triggers can also be used to prevent unwanted updates.

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  • They can be used to add a timestamp when tables are updated.

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Subselects / Nested Queries

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Views:

  • Views are used to create a copy with the intent of data manipulation and exploration.

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And one last nifty thing to remember when dealing with times.

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