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In order for a SQL statement to be parsed, the table and column names involved must be known. So the table name can't be represented by a bind variable, because the value would not be known at parse time.
The UNION operator is a set operator that combines result sets of two or more SELECT statements into a single result set. The following illustrates the syntax of the UNION operator that combines the result sets of two queries: SELECT column_list_1 FROM T1 UNION SELECT column_list_1 FROM T2; Code language: SQL (Structured Query Language) (sql)
The syntax for the UNION operator in Oracle/PLSQL is: SELECT expression1, expression2, ... expression_n FROM tables [WHERE conditions] UNION SELECT expression1, expression2, ... expression_n FROM tables [WHERE conditions];
The UNION operator returns only distinct rows that appear in either result, while the UNION ALL operator returns all rows. The UNION ALL operator does not eliminate duplicate selected rows:
UNION ALL Syntax. The UNION operator selects only distinct values by default. To allow duplicate values, use UNION ALL: SELECT column_name (s) FROM table1. UNION ALL. SELECT column_name (s) FROM table2; Note: The column names in the result-set are usually equal to the column names in the first SELECT statement.
25 Σεπ 2018 · Syntax: The syntax for the Union vs Union All operators in SQL is as follows: SELECT Column1, Column2, … ColumnN FROM <table> [WHERE conditions] [GROUP BY Column(s]] [HAVING condition(s)] UNION SELECT Column1, Column2, … ColumnN FROM table [WHERE condition(s)]; ORDER BY Column1,Column2… Rules: There are a few rules that apply to all set ...
8 Αυγ 2017 · With query_name (Id, Name, Surname) AS ( Select ID, Name, Surname FROM table_1 UNION ALL Select ID, Name, Surname FROM table_2 UNION ALL Select ID, Name, Surname FROM table_3 UNION ALL --... --all the other tables ) SELECT * FROM query_name WHERE Name = "John"
