У плюсика есть ряд ограничений
FM
Oracle Corporation recommends that you use the FROM clause OUTER JOIN syntax rather than the Oracle join operator. Outer join queries that use the Oracle join operator (+) are subject to the following rules and restrictions, which do not apply to the FROM clause join syntax:
You cannot specify the (+) operator in a query block that also contains FROM clause join syntax.
The (+) operator can appear only in the WHERE clause or, in the context of left-correlation (that is, when specifying the TABLE clause) in the FROM clause, and can be applied only to a column of a table or view.
If A and B are joined by multiple join conditions, then you must use the (+) operator in all of these conditions. If you do not, then Oracle will return only the rows resulting from a simple join, but without a warning or error to advise you that you do not have the results of an outer join.
The (+) operator does not produce an outer join if you specify one table in the outer query and the other table in an inner query.
You cannot use the (+) operator to outer-join a table to itself, although self joins are valid. For example, the following statement is not valid:

-- The following statement is not valid:
SELECT employee_id, manager_id
FROM employees
WHERE employees.manager_id(+) = employees.employee_id;


However, the following self join is valid:

SELECT e1.employee_id, e1.manager_id, e2.employee_id
FROM employees e1, employees e2
WHERE e1.manager_id(+) = e2.employee_id;


The (+) operator can be applied only to a column, not to an arbitrary expression. However, an arbitrary expression can contain one or more columns marked with the (+) operator.
A condition containing the (+) operator cannot be combined with another condition using the OR logical operator.
A condition cannot use the IN comparison condition to compare a column marked with the (+) operator with an expression.
A condition cannot compare any column marked with the (+) operator with a subquery.

If the WHERE clause contains a condition that compares a column from table B with a constant, then the (+) operator must be applied to the column so that Oracle returns the rows from table A for which it has generated nulls for this column. Otherwise Oracle will return only the results of a simple join.

In a query that performs outer joins of more than two pairs of tables, a single table can be the null-generated table for only one other table. For this reason, you cannot apply the (+) operator to columns of B in the join condition for A and B and the join condition for B and C.2) Сталкивался с таким.

2 Sash

- Операция (+) не выполнит внешнее соединение,если одна таблица указана во внешнем запросе,а другая во внутреннем.
- Операция (+) может применяться только к столбцам,но не к произвольным выражениям.Однако произвольные выражения могут содержать один или несколько столбцов с операцией (+)
- Условие,содержащее операцию (+) нельзя обьединять с другим условием с помощью оператора OR
- Условие не может использовать операцию сравнения IN для сравнения столбца,отмеченного операцией (+) с выражением
- Условие не может сравнивать столбец,отмеченный операцией (+) с подзапросом


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