When using a function like CONVERT_TZ() to convert between time zones in MySQL, we provide the date/time value, along with the original time zone and the destination time zone (i.e. the time zone that we’re converting to).
One typical way to do this is to use the time zone offset, such as −05:00 to specify the time zone. Another method is to use the time zone name. However, this requires that we have configured named time zones in MySQL.
If you’re getting an error that reads something like “START value (101) cannot be greater than MAXVALUE (100)” in PostgreSQL when you’re trying to create a sequence, it’s probably because your sequence’s maximum possible value is lower than the start value.
To fix this issue, change either the start value or maximum value so that the maximum value is greater than the start value.
Continue readingIn MySQL, we can use the ->> operator to extract a value from a JSON document, and unquote that value.
We provide the column that contains the JSON document to the left of the operator, and the path to the value that we want to extract to the right.
The ->> operator is equivalent to JSON_UNQUOTE(JSON_EXTRACT()), and it provides the same results.
In MySQL, we can use the -> operator to extract data from a JSON document.
We provide the column that contains the JSON document to the left of the operator, and the path to the value that we want to extract to the right.
The -> operator is an alias for the two-argument form of the JSON_EXTRACT() function.
When using the FOR XML clause in a query in SQL Server, we can generate an XML document either with or without an inline schema.
To generate it with an inline XSD schema simply include the XMLSCHEMA argument. We can alternatively include the namespace if we want to specify a particular namespace.
At the time of writing, the XMLSCHEMA argument is only available when in either AUTO or RAW mode.
In MySQL, the MEMBER OF() operator tests whether or not a value is a member of a given JSON array.
It returns true (1) if the array contains the value, and false (0) if it doesn’t.
The MEMBER OF() operator was added in MySQL 8.0.17.
If you’re getting an error in PostgreSQL that reads something like “cannot insert into column” with detail that explains that the “…is an identity column defined as GENERATED ALWAYS“, it’s probably because you’re trying to insert your own value into an identity column that was created with the GENERATED ALWAYS option, but you’re not explicitly overriding the column from auto generating its own value.
To fix this issue, use OVERRIDING SYSTEM VALUE when inserting the value.
In MySQL, JSON_OVERLAPS() is a function that tests whether or not two JSON documents have any key-value pairs or array elements in common.
The function returns true (1) if the documents have any key-value pairs or array elements in common, and false (0) if they don’t.
The JSON_OVERLAPS() function was added in MySQL 8.0.17.
If you’re getting an error that reads something like “ERROR 1050 (42S01) at line 22: Table ‘Pets’ already exists” when trying to create a table in MariaDB, it’s most likely because there’s already a table in the database with the same name.
To fix this issue, either change the name of the table you’re trying to create, or check the existing table to see if it’s the one you actually need.
Continue readingIn MySQL, JSON_MERGE() is a deprecated function that merges two or more JSON documents and returns the result.
It was deprecated in MySQL 8.0.3 and is subject to removal in a future release.
Fortunately, the JSON_MERGE_PRESERVE() function was added in MySQL 8.0.3 as a synonym for JSON_MERGE(), and it therefore does the same thing that JSON_MERGE() does/did.
Therefore, instead of using JSON_MERGE(), use JSON_MERGE_PRESERVE() instead.
Alternatively, you can use JSON_MERGE_PATCH(), which performs an RFC 7396 compliant merge of two or more JSON documents, without preserving members having duplicate keys.