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25 Ιαν 2024 · An OUTER JOIN in SQL is used when you want to combine rows from two or more tables and include those rows in one table that don't have matching rows in the other table. This is the opposite of INNER JOIN , which includes only matching rows from both tables.
JOIN combines data from two tables. JOIN typically combines rows with equal values for the specified columns. Usually, one table contains a primary key, which is a column or columns that uniquely identify rows in the table (the cat_id column in the cat table).
With an outer join the columns from the table where data is "missing" are returned as NULL values. Outer joins come in two basic flavours, called Left and Right.
What Is an OUTER JOIN? As we explained in the previous chapter,the SQL Standard defines several types of JOIN operations to link two or more tables or result sets. An OUTER JOIN asks your database system to return not only the rows that match on the criteria you specify but also the unmatched rows from either one or both of the two sets you ...
OUTER JOIN • Consider the last line of the unconstrained join… • This is a car without an owner. • Sometimes we want to see the rows that fail the join condition due to NULL values. • To see NULL joins we use OUTER JOIN. • The JOIN discussed up to this point is known as INNER JOIN.
25 Φεβ 2018 · Table of Contents v Table of Contents INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 About This ...
Joining tables with INNER JOIN: SELECT * FROM facts LEFT JOIN cities ON cities.facts_id = facts.id; Joining tables using a LEFT JOIN: SELECT f.name country, c.name city FROM cities c RIGHT JOIN facts f ON f.id = c.facts; Joining tables using a RIGHT JOIN: SELECT f.name country, c.name city FROM cities c FULL OUTER JOIN facts f ON f.id = c.facts_id;
