MySQL provides us with a handy WITH ROLLUP modifier that allows us to get totals and subtotals when using the GROUP BY clause.
Below is an example of how the MySQL WITH ROLLUP modifier works.
Author: Ian
Fix Error 6358 “…is not a valid style number when converting to XML” in SQL Server
If you’re getting error msg 6358 which reads something like 300 is not a valid style number when converting to XML, it’s probably because you’re trying to convert a value to XML, but the style that you’re specifying isn’t supported for conversions to that data type.
It’s not that the conversion can’t happen, it’s just that it can’t happen using the style that you’re specifying.
Continue reading10 Functions and Operators that Search JSON Documents in MySQL
MySQL provides us with a bunch of functions and operators that allow us to search JSON documents for various things, such as specific values, paths, keys, etc.
Here are seven functions and three operators that search JSON documents in MySQL.
Continue readingUnderstanding the VAR_SAMP() Function in MySQL
In MySQL, the VAR_SAMP() function returns the sample variance of an expression. The denominator is the number of rows minus one.
If there are no matching rows, or if the expression is NULL, VAR_SAMP() returns NULL.
VAR_SAMP() is an aggregate function, and so it can be used with the GROUP BY clause.
The VAR_SAMP() function can also be used as a window function.
How VARIANCE() Works in MySQL
In MySQL, the VARIANCE() function returns the population standard variance of an expression.
If there are no matching rows, or if the expression is NULL, the function returns NULL.
The VARIANCE() function is a synonym for the standard SQL VAR_POP() function. In other words, they both do the same thing, but VARIANCE() is not standard SQL. Therefore, if you need to use standard SQL, use VAR_POP() instead.
Fix “WRONGTYPE Operation against a key holding the wrong kind of value” when using ZCOUNT in Redis
If you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the ZCOUNT command in Redis, it’s probably because you’re passing a key with the wrong data type.
To fix this issue, be sure that the key you pass to the ZCOUNT command holds a sorted set.
Understanding the VAR_POP() Function in MySQL
In MySQL, the VAR_POP() function returns the population standard variance of an expression.
If there are no matching rows, or if the expression is NULL, VAR_POP() it returns NULL.
VAR_POP() is an aggregate function, and so it can be used with the GROUP BY clause.
The VAR_POP() function is standard SQL. There’s also a VARIANCE() function that does the same thing, but is not standard SQL.
Understanding the STDDEV_SAMP() Function in MySQL
In MySQL, the STDDEV_SAMP() function returns the sample standard deviation of a given expression. This is the square root of VAR_SAMP().
STDDEV_SAMP() is an aggregate function, and so it can be used with the GROUP BY clause.
If there are no matching rows, or if the expression is NULL, STDDEV_SAMP() returns NULL.
Introduction to the STDDEV_POP() Function in MySQL
In MySQL, the STDDEV_POP() function returns the population standard deviation of a given expression.
There’s also a STD() and STDDEV() function, both of which do the same thing as STDDEV_POP().
Overview of the STDDEV() Function in MySQL
In MySQL, the STDDEV() function returns the population standard deviation of a given expression.
STDDEV() is a synonym for the standard SQL function STDDEV_POP(). There’s also a STD() function which also does the same thing, so we can use either of these functions to get the same result.