大约有 6,100 项符合查询结果（耗时：0.0114秒） [XML]
Storing time-series data, relational or non?
... clause, it is very fast, and the query does not depend on the size of the table (grabbing 1,000 rows from a 16 billion row table is instantaneous).
Your table has one serious impediment. Given your description, the actual PK is (Device, Metric, DateTime). (Please don't call it TimeStamp, that mea...
Is a view faster than a simple query?
...y referenced by another query as the optimizer will use them in place of a table reference when appropriate.
Again, the documentation:
The indexed view can be used in a query execution in two ways. The query can reference the indexed view directly, or, more importantly, the query optimizer c...
How to update column with null value
...
No special syntax:
CREATE TABLE your_table (some_id int, your_column varchar(100));
INSERT INTO your_table VALUES (1, 'Hello');
UPDATE your_table
SET your_column = NULL
WHERE some_id = 1;
SELECT * FROM your_table WHERE your_column IS NULL;
+---...
How to import an excel file in to a MySQL database
... Note that this procedure requires that you first create the table, with the appropriate fields.
– LarsH
Mar 24 '16 at 15:00
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Log all queries in mysql
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Is it possible to log queries over 1 particuarl db / table only?
– Temujin
Aug 4 '12 at 16:08
2
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Equivalent of LIMIT and OFFSET for SQL Server?
... ROW_NUMBER() OVER (ORDER BY SortCol1, SortCol2, ...) AS RowNum
FROM Table
WHERE <whatever>
)
SELECT *
FROM Results_CTE
WHERE RowNum >= @Offset
AND RowNum < @Offset + @Limit
The advantage here is the parameterization of the offset and limit in case you decide to change your p...
How to show the last queries executed on MySQL?
...ontrol this option globally at runtime:
Execute SET GLOBAL log_output = 'TABLE';
Execute SET GLOBAL general_log = 'ON';
Take a look at the table mysql.general_log
If you prefer to output to a file instead of a table:
SET GLOBAL log_output = "FILE"; the default.
SET GLOBAL general_log_file = ...
Rails migration: t.references with alternative name?
So I have a create_table like this for Courses at a School:
5 Answers
5
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Liquibase lock - reasons?
...inst the database helps.
Or you can simply drop the DATABASECHANGELOGLOCK table, it will be recreated.
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Fastest way to determine if record exists
...e fastest way with the least overhead to determine if a record exists in a table or not.
11 Answers
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