Step Snap 1 [JOIN Syntax Variations]:

SQL Advanced Query Operations and Data Analysis

Step Snap 1 [JOIN Syntax Variations]: There are two main syntaxes for table joins in SQL:

1. Using WHERE clause (Traditional syntax):

SELECT t.column1, t.column2
FROM table1 t, table2 z
WHERE t.id = z.id

1. Using JOIN keyword (Recommended syntax):

SELECT t.column1, t.column2
FROM table1 t
JOIN table2 z ON t.id = z.id

Key differences:

• JOIN syntax more clearly expresses relationships between tables
• JOIN syntax supports more join types (LEFT, RIGHT, OUTER, INNER)
• WHERE syntax can become less intuitive in complex queries

Step Snap 2 [JOIN Types and Data Integrity]:

Different JOIN types for various scenarios:

-- INNER JOIN (default): returns only matching rows
FROM table1 t JOIN table2 z ON t.id = z.id

-- LEFT JOIN: keeps all rows from left table
FROM table1 t LEFT JOIN table2 z ON t.id = z.id

-- RIGHT JOIN: keeps all rows from right table
FROM table1 t RIGHT JOIN table2 z ON t.id = z.id

-- FULL OUTER JOIN: keeps all rows from both tables
FROM table1 t FULL OUTER JOIN table2 z ON t.id = z.id

Data integrity check example:

-- Check for missing related records
SELECT *
FROM table1
WHERE id NOT IN (SELECT id FROM table2)

Step Snap 3 [Date Operations and Aggregations]: