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When to use single quotes, double quotes, and backticks in MySQL
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Backticks are to be used for table and column identifiers, but are only necessary when the identifier is a MySQL reserved keyword, or when the identifier contains whitespace characters or characters beyond a limited set (see below) It is often recommende...
MySQL foreign key constraints, cascade delete
...illed, then you've set up your foreign keys improperly. Given your example tables, you should have the following table setup:
CREATE TABLE categories (
id int unsigned not null primary key,
name VARCHAR(255) default null
)Engine=InnoDB;
CREATE TABLE products (
id int unsigned not null ...
How to shrink/purge ibdata1 file in MySQL
... is, everytime I run a R script, I create a new database (A), create a new table (B), import the data into B, submit a query to get what I need, and then I drop B and drop A.
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SQL Server : Columns to Rows
...nto rows:
select id, entityId,
indicatorname,
indicatorvalue
from yourtable
unpivot
(
indicatorvalue
for indicatorname in (Indicator1, Indicator2, Indicator3)
) unpiv;
Note, the datatypes of the columns you are unpivoting must be the same so you might have to convert the datatypes prior t...
How can I hide an HTML table row so that it takes up no space?
How can I hide an HTML table row <tr> so that it takes up no space? I have several <tr> 's set to style="display:none;" , but they still affect the size of the table and the table's border reflects the hidden rows.
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CSS Cell Margin
In my HTML document, I have a table with two columns and multiple rows. How can I increase the space in between the first and second column with css? I've tried applying "margin-right: 10px;" to each of the cells on the left hand side, but to no effect.
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How to select the last record of a table in SQL?
This is a sample code to select all records from a table. Can someone show me how to select the last record of that table?
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Programmatically creating Markdown tables in R with KnitR
...ver, one thing that I'm not seeing is an easy way to print data frames and tables using Markdown formatting (sort of like xtable , but with Markdown instead of LaTeX or HTML). I know that I can just embed the HTML output from xtable, but I was wondering if there were any Markdown-based solutions?
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Best way to check if a Data Table has a null value in it
what is the best way to check if a Data Table has a null value in it ?
6 Answers
6
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Group by & count function in sqlalchemy
... is better to use func.count():
from sqlalchemy import func
session.query(Table.column, func.count(Table.column)).group_by(Table.column).all()
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