Database Management Systems
Starting from MongoDB 4.4, we can now hide indexes from the query plan. This enables us to evaluate the potential impact of dropping an index without actually dropping the index.
If hiding it has a negative impact, we can unhide the index. This saves us from having to drop the index, then recreate it again.
Below are 3 ways to hide an index in MongoDB.
Continue readingIf you’re trying to use OPENROWSET to run an ad hoc distributed query in SQL Server, but you keep getting an “incorrect syntax” error, and you just can’t see anything wrong with your syntax, it could be that you’re trying to use a variable for one of the arguments.
As mentioned in the title of this post, OPENROWSET does not accept variables for its arguments.
If you’re using variables as arguments, try changing these to string literals.
Continue readingIn MariaDB, the REGEXP_REPLACE() function replaces occurrences of the substring within a string that matches the given regular expression pattern.
The whole string is returned along with the replacements.
If there’s no match (i.e. the input string doesn’t contain the substring), the the whole string is returned unchanged.
Continue readingIn MariaDB, the REGEXP_SUBSTR() function returns the substring that matches the given regular expression pattern.
If there’s no match (i.e. the input string doesn’t contain the substring), the result is an empty string.
Continue readingIn MariaDB, the REGEXP_INSTR() function returns the starting index of a substring that matches the regular expression pattern.
The index starts at 1. If there’s no match, the result is 0.
In MariaDB, NOT RLIKE is a negation of the RLIKE operator.
In other words, any time the RLIKE operator would return 1, NOT RLIKE will return 0.
In MariaDB, the RLIKE operator is used to determine whether or not a string matches a regular expression. It’s a synonym for REGEXP.
If the string matches the regular expression provided, the result is 1, otherwise it’s 0.
In MariaDB, the NOT REGEXP operator is a negation of the REGEXP operator.
If the string matches the regular expression provided, the result is 0, otherwise it’s 1. This is the opposite result to what the REGEXP would return (when it isn’t prefixed with NOT).
In MariaDB, the REGEXP operator is used to determine whether or not a string matches a regular expression.
If the string matches the regular expression provided, the result is 1, otherwise it’s 0.
The 10.6.0 release of MariaDB has added a JSON_TABLE() function.
The JSON_TABLE() function returns a representation of a JSON document as a relational table with the specified columns. It enables you to map JSON paths into relational columns to be returned in its results set.