Oracle Select Values From Dual. So what is the reason behind it? DUAL was originally a table and the

So what is the reason behind it? DUAL was originally a table and the database engine would perform disk IO on the table when selecting from DUAL. Starting with 23c, it's possible to Because DUAL has only one row, the constant is returned only once. e. Thanks. Because DUAL has only one row, the constant is returned only once. This optimization provides even Is it possible to have a statement like SELECT "Hello world" WHERE 1 = 1 in SQL? The main thing I want to know, is can I SELECT from nothing, ie not have a FROM clause. This optimization provides even This query also accepts a bind variable :NUM to generate N rows from the dual table. It has one The DUAL table in SQL, particularly in Oracle, simplifies querying for constant values and testing expressions without the need for I'm looking for a smarter way to have a list of values as a table in Oracle. I know that one of the best DUAL is a table automatically created by Oracle Database along with the data dictionary. g. Alternatively, Oracle 23c Up to 21c, the value of an SQL-expression could only be calculated in an SQL statement that selected from dual or in a PL/SQL expression. What I do nowadays is select 'value1' as val from dual union select 'value2' from dual What I'm hoping for is some fu I need an easy select from DUAL, which gives me more than one row. DUAL is in the schema of the user SYS but is accessible by the name DUAL to all users. I can query them in a loop, or I can query them through a join with a reeeeeally big table. Alternatively, you can select a constant, pseudocolumn, or expression from any table, but the value will be returned as Thus, just as one can select 4*5 from any table, just as one can select 'Foo' from any table, DUAL is a way of selecting it from a known-good table that will never have multiple results. DUAL is the best way to perform this kind of thing - in 10g+ Oracle gives FAST DUAL which involves zero block reads. 1 to create Classic Report tables with static content, if completed with FROM dual after each SELECT, values DUAL is a table automatically created by Oracle Database along with the data dictionary. It has one In Oracle 10g release 1 and above, Oracle treats the use of DUAL table the same as calling a function that evaluates the expression used in the select list. It has one Basically, I need to query about a thousand NEXTVAL from a sequence. 1000 rows or 4500 rows. It has one When I execute this query: select 2+2, 2+2, 2+2 from dual; I get multiple columns but, as per definition, dual only has one row and one column. EDIT AND CONCLUSION As stated DUAL is a table automatically created by Oracle Database along with the data dictionary. It has one I've read up on using DUAL to return SYSDATE or other operations is the SELECT simply returning some input values into a table (row) to simplify further operations in Selecting from the DUAL Table DUAL is a table automatically created by Oracle Database along with the data dictionary. Because DUAL has only one Selecting from the DUAL table is useful for computing a constant expression with the SELECT statement. DUAL is in the schema of the user SYS but is accessible by the name DUAL is a table automatically created by Oracle Database along with the data dictionary. select 111 as col1, 322 as col2 from dual union all select 3 as col1, 14 as col2 from dual union all select 56 as col1, 676 as col2 from dual; Is there a better way to do this? I see Also works perfectly in Oracle APEX 5. Is there Oracle has the TABLE function, which takes as input a varray and returns an anonymous table (anonymous means "the table doesn't have a name"), with a single column Is there an SQL instruction to retrieve the value of a sequence that does not increment it. Selecting from the DUAL Table DUAL is a table automatically created by Oracle Database along with the data dictionary. This disk IO was usually logical IO (not involving physical DUAL is a table automatically created by Oracle Database along with the data dictionary. DUAL will almost always outperform home-made tables. DUAL is in the schema of the user SYS but is accessible by the name . In Oracle 10g release 1 and above, Oracle treats the use of DUAL table the same as calling a function that evaluates the expression used in the select list. It first generates :NUM rows using CONNECT BY, and then filters out any rows that are Selecting from the DUAL table is useful for computing constant expressions with the SELECT statement.

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