Reading-Notes
A Basic Guide to SQL
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Select query with constraints
SELECT column, another_column, …
FROM mytable
WHERE condition
AND/OR another_condition
AND/OR …;
Operators:
- =, !=, < <=, >, >=
- BETWEEN … AND …
- NOT BETWEEN … AND
- IN (…)
-
NOT IN (…)
- LIKE
- NOT LIKE
- %
- _
All strings must be quoted
Select query with unique results
SELECT DISTINCT column, another_column, …
FROM mytable
WHERE condition(s)
ORDER BY column ASC/DESC
LIMIT num_limit OFFSET num_offset
INNER JOIN another_table
> ON mytable.id = another_table.id
-
INNER/LEFT/RIGHT/FULL JOIN
-
IS/NOT/NULL
### Queries with Expressions
- Lesson 9-12 to ref directly per website
Insert statement with specific columns
INSERT INTO mytable
(column, another_column, …)
VALUES (value_or_expr, another_value_or_expr, …), (value_or_expr_2, another_value_or_expr_2, …), …;
Update statement with values
UPDATE mytable
SET column = value_or_expr, other_column = another_value_or_expr, …
WHERE condition;
Delete statement with condition
DELETE FROM mytable
WHERE condition;
Create table statement w/ optional table constraint and default value
CREATE TABLE IF NOT EXISTS mytable
( column DataType TableConstraint DEFAULT default_value, another_column DataType TableConstraint DEFAULT default_value, … );
Altering table to add new column(s)
ALTER TABLE mytable
ADD column DataType OptionalTableConstraint
DEFAULT default_value;
Altering table to remove column(s)
ALTER TABLE mytable
DROP column_to_be_deleted;
Altering table name
ALTER TABLE mytable
RENAME TO new_table_name;
Drop table statement
DROP TABLE IF EXISTS mytable;
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