Temporary tables: Like normal tables, there is a structure, but the management of the data is not the same, the temporary table stores the transaction or the intermediate result set of the session, the data saved in the temporary table is only
Count1) with Count (*) Comparison: If your data table does not have a primary key, COUNT (1) than COUNT (*Fast If there is a primary key, then the primary key (the Federated primary key) as the count condition is also more than count (*) to be quick
After listening to nearly 20 speeches in the last two days, I felt a lot of harvest, and the deepest feeling was that I still had a long way to go. There are several points to note:Listening to the old cat yesterday, it is a common problem that
Use BINARY_CHECKSUM to detect changes in the table's rows without USEAdventureWorks2012; GOCREATETABLEmyTable (column1int, column2varchar (256); values (1, test); values (*) frommyTable; GOUPDATEmyTablesetcolumn2
Using BINARY_CHECKSUM to detect
1) count (1) compared to COUNT (*):1. If your data table does not have a primary key, then count (1) is faster than COUNT (*)2, if there is a primary key, then the primary key (Union primary key) as the count of the condition is also faster than
A friend and I talked to a case, a tablespace originally had a data file (already has a lot of data entered), then he added 7 data files, this time he found that he added more files, want to delete these data files, but do not understand the
SQL Optimization-count, table join sequence, conditional order, in, exist, countexist
1. About count
I have read some articles about count (*) and count (Column). Is the efficiency of count (column) higher than that of count?
In fact, I personally
First, about CountHaving read some articles about count (*) and Count (column), is the efficiency of Count (column) certainly higher than count (*)?In fact, the individual think that count (*) and Count (column) is not comparable at all, COUNT (*)
It takes only 6 minutes to scan a 166G table from an oracle full table, and oracle166g
How can I maximize the cpu usage? How to quickly scan a large table. If a large table has a primary key, count (*) takes the primary key. oracle only needs to
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