Implicit Join and Explicit Join are two different syntaxes used in SQL queries to join multiple tables. The difference between them is mainly reflected in the writing style and readability of the grammar.
Implicit connection:
Implicit connection uses commas, puts multiple table names in the FROM clause, and connects tables in the WHERE clause through conditions. This style of join may be convenient for simple queries, but it reduces readability, is prone to errors, and is difficult to maintain in complex queries.
Example:
sql
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SELECT Orders.OrderID, Customers.CustomerName
FROM Orders, Customers
WHERE Orders.CustomerID = Customers.CustomerID;
Explicit connection:
Explicit connection uses the JOIN keyword to connect multiple tables, expressing the relationship between tables more clearly. Common join types are INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN. This way of joining allows for more explicit specification of join conditions, making queries more readable, understandable, and more maintainable when dealing with complex situations.
Example:
sql
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SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
In summary, although implicit joins may be more concise in some cases, explicit joins are generally recommended because they provide a clearer, more readable and maintainable way of querying, especially when dealing with complex query scenarios time is more favorable.
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