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COUNT(*) vs. COUNT(1) vs. COUNT(pk): which is better? [duplicate]
...OUNT(*), and stick with it consistently, and if your database allows COUNT(tableHere) or COUNT(tableHere.*), use that.
In short, don't use COUNT(1) for anything. It's a one-trick pony, which rarely does what you want, and in those rare cases is equivalent to count(*)
Use count(*) for counting
U...
Is there a performance difference between CTE , Sub-Query, Temporary Table or Table Variable?
...o use query hints, restructure the query, update statistics, use temporary tables, add indexes, and so on to get better performance.
As for your question. The performance of CTEs and subqueries should, in theory, be the same since both provide the same information to the query optimizer. One diff...
How to set a default value for a datetime column to record creation time in a migration?
Consider the table creation script below:
7 Answers
7
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How to add multiple columns to a table in Postgres?
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Try this :
ALTER TABLE table ADD COLUMN col1 int, ADD COLUMN col2 int;
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Datatables: Cannot read property 'mData' of undefined
I have an issue with Datatables . I also went through this link which didn't yield any results. I have included all the prerequisites where I'm parsing data directly into the DOM. Kindly help me to fix this issue.
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What is the simplest SQL Query to find the second largest value?
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SELECT MAX( col )
FROM table
WHERE col < ( SELECT MAX( col )
FROM table )
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How can I copy data from one column to another in the same table?
Is it possible to copy data from column A to column B for all records in a table in SQL?
3 Answers
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Copy data into another table
How to copy/append data from one table into another table with same schema in SQL Server?
9 Answers
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Is there a better way to dynamically build an SQL WHERE clause than by using 1=1 at its beginning?
... offer you:
using (var dbContext = new MyDbContext())
{
IQueryable<Table1Item> query = dbContext.Table1;
if (condition1)
{
query = query.Where(c => c.Col1 == 0);
}
if (condition2)
{
query = query.Where(c => c.Col2 == 1);
}
if (condition3)...
MySQL maximum memory usage
...the (f'ing) manual.
As for the database -- a few important constraints:
table engine (InnoDB, MyISAM, ...)
size
indices
usage
Most MySQL tips on stackoverflow will tell you about 5-8 so called important settings. First off, not all of them matter - e.g. allocating a lot of resources to InnoDB a...