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25 mar 2016 · You can use multiple left joins to get the data from both tables, then use an IF () to determine which of the column (s) you want as your result. SELECT *, IF (users.type = 1, p.name, c.name) AS name FROM users. LEFT JOIN private AS p ON (users.type = 1 AND users.id = p.user_id)
Approach 2 - LEFT OUTER JOIN. It is possible to get the same result without UNION: SELECT IFNULL (p. name, p2. name) FROM contestParticipants c. LEFT OUTER JOIN persons p ON (c. participant_id = p. id AND c. participant_type = 'P') LEFT OUTER JOIN teamPersons tp ON (c. participant_id = tp. team_id AND c. participant_type = 'T') ...
The INNER JOIN clause compares each row in the t1 table with every row in the t2 table based on the join condition. If rows from both tables cause the join condition to evaluate to TRUE, the INNER JOIN creates a new row whose columns
The LEFT JOIN clause selects data starting from the left table (t1), matching each row from the left table (t1) with every corresponding row from the right table(t2) based on the join_condition. If the rows from both tables satisfy the join condition, the left join combines columns from both tables into a new row and includes this new row in ...
23 lip 2024 · There are two algorithms to compute natural join and conditional join of two relations in database: Nested loop join, and Block nested loop join. To understand these algorithms we will assume there are two relations, relation R and relation S. Relation R has TR tuples and occupies BR blocks.
9 cze 2016 · FROM table1 LEFT JOIN table2 ON table1.column_id = table2.column_id WHERE table2.column LIKE '%$variable%' RESULT 1 If $variable has no value, only rows with respective data from table2 are displaying.
8 kwi 2012 · Specify the condition as part of the ON clause: SELECT m.id, u.first_name AS otherUser. FROM matches AS m. LEFT JOIN users AS u ON (u.id=m.user2ID and u.id = m.user1ID) or (u.id<>m.user2ID and u.id = m.user2ID) . WHERE m.user1ID=2 OR m.user2ID=2. Another way to do the same thing: SELECT m.id, u.first_name AS otherUser. FROM matches AS m.
