DolphinDB is a high performance time series database. It is written in C++ and optimized for fast injection, storage, retrieval and analysis of time series data in fields such as quantitative finance, Internet of Things, real-time analytics, etc. DolphinDB runs extremely fast. It is also easy to use as the syntax of the programming language of DolphinDB is similar to SQL and Python.
Questions tagged [dolphindb]
764 questions
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How to check the execution state of “scheduledJob”?
How to check the execution state of “scheduledJob”?
How to check whether the function “scheduledJob” execute completely or not?
damie
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1 answer
What is the minimum interval to execute the function “scheduledJob”?
What is the minimum interval to execute the function “scheduledJob”?
What is the minimum interval to execute a scheduled job? Is it 10 minutes? Or 20 minutes?
damie
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1 answer
The error of “The key type can't be BOOL, ANY or DICTIONARY”
I run the following scripts in DolphinDB database GUI:
x=(int128("2e8ca9773da3a99f2c87a623ac34f242"),int128("2e8ca9773da3a99f2c87a623ac34f243"))
y=1..2
dict(x, y);
It returns me an exception:
dict(x, y) => The key type can't be BOOL,…
damie
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1 answer
How to get the latest record for each device in DolphinDB?
I create a streaming table named device in DolphinDB to store the real-time data for 3000 devices. Now I want to query the last record for each device. How to write the sql statement?
The structure of this streaming table is as below:
Name …
user15518852
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1 answer
undefined reference to `SSL_library_init' error during the compiling for C++ API
undefined reference to `SSL_library_init' error during the compiling for C++ API
The OpenSSL version I used is 1.1.1, and the error is:
../bin/linux_x64/ABI0/libDolphinDBAPI.so: undefined reference to…
user15518852
1
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1 answer
Assign a new value to a specified column in a table
Assign a new value to a specified column in a table
Which function can be used to assign a new value to a specified column? Take an example: I have a table names t. If I query a element in row1 and column0, I can invoke t.cell(1, 0). But seems it…
user15518852
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1 answer
Why an empty table consumes memory in dolphindb?
Why an empty table consumes memory in dolphindb?
I create an empty table, the code is:
colName = ["time", "x"]
colType = ["timestamp", "int"]
t = table(1000000:0, colName, colType);
pnodeRun(objs)
I find the empty table also consumes memory, why?
user15518852
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1 answer
Is there any difference between count(*) and count(column) in dolphindb?
Is there any difference between count(*) and count(column) in dolphindb?
What's the difference in their performance?
damie
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How to improve the calculation speed of minute OHLC？
The code provided in the DolphinDB finance example suggests that the MR function in MapReduce is used to improve efficiency.
`model=select top 1 symbol,date, minute(time) as minute, open, high, low, last, curVol as volume from quotes where…
user15518852
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1 answer
How to add a column to the established streaming table？
already had a streaming table, some data has been written in.
now i need to add a column.
sample here:
n=10
ticker = rand(`MSFT`GOOG`FB`ORCL`IBM,n)
x=rand(1.0, n)
t=streamTable(ticker, x)
share t as st
ctreated a streaming table which only have X…
user15504166
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1 answer
problem with using datehour() function in DolphinDB
codes in GUI:
datehour(2018.09.03 8:30:00)
runtime error:
2020.12.09 17:14:24.420: executing code ...
Both arguments of 'pair' must be a scalar
why?
user15504166
1
vote
1 answer
how to query if a column is named as a keyword in dolphindb?
had a table contains a column named true in pic below
[enter image description here][1]
and code like
select true from t
error : Syntax Error: [line #1] A table column [1] must be assigned a valid name.
why?
[1]: https://i.stack.imgur.com/k6lna.png
damie
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how to eliminate duplicate records from a distributed table in a DolphinDB query
I used the following script to delete duplicate records from the query result in DolphinDB where 'quotes' is a distributed table with 2 partitioning columns 'date' and 'symbol'.
select * from quotes where date=2020.12.10 and isDuplicated([date,…
ftsd
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List Tables in a DolphinDB database
What is the equivalent to SHOW TABLES in DolphinDB?
yannyz_coopoo
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1 answer
How to create a list of months in DolphinDB?
I need to generate a list containing all months between Jan 2020 and Jan 2023,
The result should be as follows:
[2020.01, 2020.02, ..., 2023.01]
How can I get this in DolphinDB?
Thanks!
a._dash
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