The problem is that in a situation when the table pages are not in memory, or simply the table is bigger than the buffer pool, using parallel threads results in way more disk reads versus when one thread is used. This means the same operation is now much more expensive! Unfortunately, th...
i want to know what does SELECT ANY DICTIONARY really mean. I want to know what i am actually granting if I give out that privilege; well it means access to 6228 tables and views in 18cXE
openGauss=# create table test(name varchar, id int, fatherid int); openGauss=# insert into test values('A', 1, 0), ('B', 2, 1),('C',3,1),('D',4,1),('E',5,2); openGauss=# select * from test start with id = 1 connect by prior id = fatherid order siblings by id ...
The 3rdsimilar syntax is the UNIQUE constraint which is different from than SELECT UNIQUE which I explained above. The UNIQUE constraint is used while creating a table and mentioning it as a constraint for a column or set of columns to store only unique values and prevent duplicate values to ...
This means: If the expanded object has a property of the same name, the command returns an error. If the Selected object has a property of the same name as an Expanded object's property, the command returns an error. Expand table Type: String Position: Named Default value: None ...
SELECTa,b,COUNT(c)AStFROMtest_tableGROUPBYa,bORDERBYa,tDESC; As of MySQL 8.0.13, theGROUP BYextension is no longer supported:ASCorDESCdesignators forGROUP BYcolumns are not permitted. When you useORDER BYorGROUP BYto sort a column in aSELECT, the server sorts values using only the initial...
If you are selecting from a table rather than from a view or a materialized view, then columns that have been marked asUNUSEDby theALTERTABLESETUNUSEDstatement are not selected. See Also: ALTER TABLE,"Simple Query Examples", and"Selecting from the DUAL Table: Example " ...
A Database_Cached object however fetches all rows from the result at once, and stores it in the object. This means that, depending on the size of the resultset, it might have quite a substantial memoty footprint. But the plus side is, it allows you random access to the rows retrieved...
[offset,] count | ALL } ] [ OFFSET start [ ROW | ROWS ] ] [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ] [ {FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NOWAIT | WAIT n | SKIP LOCKED ]} [...] ] TABLE { ONLY { (table_name) | table_...
[FirstName],COUNT(1)AS RowCnt FROM [Person].[Person] WHERE [FirstName]LIKE'Rob%'GROUP BY [FirstName] HAVINGCOUNT(1)>=20 Selecting data from multiple SQL Server tables Often you don’t need data from one single table, but you’ll need to combine different tables to get the result you...