databases

SQLite “cheat sheet”

Tips!

1. SQL is not case sensitive
2. End each SQL statement with a semicolon “;”
3. Use “*” to select an entire record
4. White space doesn’t matter
5. SELECT statement is like creating a new table
6. Field value needs to be in quotes
7. Use parentheses to force order of operations
8. Use two hyphens “–” to comment

C.R.U.D.

Create

1. CREATE DATABASE db_name - creates a database

2. CREATE TABLE table_name (field_name DATA_TYPE CONSTRAINTS) - creates a table in the database

3. Data types

1. `DATE`

2. `TIME`

3. `TIMESTAMP`

4. `VARCHAR/CHARACTER`

5. `BOOLEAN`

6. `INTEGER`

7. `DOUBLE PRECISION (FLOAT)`

8. `XML`

1. Constraints

1. `PRIMARY KEY`

2. `FOREIGN KEY`

3. `UNIQUE`

4. `DEFAULT`

5. `AUTOINCREMENT`

6. `NOT NULL`

1. INSERT INTO table_name(field1, field2) VALUES ('value1', 'value2') - insert data into a table for one record

2. INSERT INTO table_name(field1) VALUES (record1), (record2), (record3) - insert data into a table for multiple records

Read

This is the basic format for querying a database

1. SELECT field1, field2 - select fields to return (or * to return entire record)

2. FROM table_name - select the table

3. INNER JOIN table1, table2 - specify which tables to pull data from

4. ON table1.field_a = table2.field_b - specify which records to return from the join operation (JOIN + ON creates a temporary table that includes data from table1 and table2 for only those records where the value in table1.field_a is equal to the value in table2.field_b)

5. WHERE table.field_a = "value_x" - only returns records whose value for field_a is equal to value_x (WHERE acts like filter)

   1. WHERE table.field_a IN ("value_x", "value_y", "value_z") - only return records whose value for field_a is one of values in the parentheses (NOT IN - does the opposite)

   2. WHERE table.field_a = value_x AND table.field_b = value_y - only returns records where both conditions are met

   3. ... field_a = value_x OR field_b = value_y

   4. ... field_a BETWEEN value_x AND value_y

   5. ... field_a LIKE "spa%" - return only records whose value in field_a starts with “spa”

   6. <, <=, >, >=, !=

   7. BETWEEN

   8. IS - equal to a value (or empty for IS NULL)

   9. IS NOT - is not equal to a value (or is not empty for IS NOT NULL)

6. ORDER BY field_a ASC/DESC - format how results are displayed - arrange records returned by values in field_a according to ascending order (DESC for descending order)

Misc.

1. SELECT DISTINCT field_a FROM table - return only distinct values for field_a

2. SELECT COUNT(*) FROM table - return the number of records in the table

3. SELECT * FROM table LIMIT 5 - return only the first 5 records from the table

Update

1. ALTER TABLE table_name RENAME TO new_table_name - rename a table

2. ALTER TABLE table_name ADD COLUMN new_field_name DATA_TYPE CONSTRAINTS - add a new field to a table (include data type and field constraints)

3. UPDATE table SET field_a = value_x WHERE field_b = value_y - add new data to one or more fields in a table

Delete

1. DELETE FROM table WHERE field = value - delete data from a table

2. DROP TABLE table_name - delete a whole table

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