PostgreSQL 中的加等于运算符是什么？

Question

在 Oracle SQL 中，有一个 (+)= 运算符可以添加等号。

我一直在网上搜索但无法找到 PostgreSQL 语法的等效项，PostgreSQL 中是否存在此运算符？如果没有，我将如何实现相同的功能？

提前致谢。

Answer 1

Oracle 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 OUTER 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 (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 Database 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.

注意：在 Oracle PL/SQL 中既没有 += 也没有 +:= 运算符：

SQL> declare
  2  i numeric := 0;
  3  begin
  4   i+:=1;
  5  end;
  6  /
 i+:=1;
  *
ERROR at line 4:
ORA-06550: line 4, column 3:
PLS-00103: Encountered the symbol "+" when expecting one of the following:
:= . ( @ % ;
The symbol "+" was ignored.


SQL> --
SQL> declare
  2  i numeric := 0;
  3  begin
  4   i+=1;
  5  end;
  6  /
 i+=1;
  *
ERROR at line 4:
ORA-06550: line 4, column 3:
PLS-00103: Encountered the symbol "+" when expecting one of the following:
:= . ( @ % ;


SQL> show errors
No errors.
SQL> --
SQL> declare
  2  i numeric := 0;
  3  begin
  4   i := i + 1;
  5  end;
  6  /

PL/SQL procedure successfully completed.

SQL>

PostgreSQL 中的加等于运算符是什么？

What is the add equals operator in PostgreSQL?

postgresql

outer-join