If you want to use named time zones in MySQL, you’ll need to make sure they’ve been configured.
By “named time zones”, I mean being able to use strings like US/Eastern instead of −04:00 or −05:00 when specifying the time zone. For example, when using the CONVERT_TZ() function.
Here’s how to configure named time zones in MySQL.
Continue readingIf you’re getting error 1045 that reads something like “Access denied for user ‘root’@’localhost’“, it’s because you’re trying to log in to MySQL without the right credentials.
This usually happens when we provide the wrong password. But there could also be another cause. For example, we could be trying to do something as the root user that requires a password, but the root user hasn’t yet had its password set.
To fix this issue, be sure to provide the correct password when connecting to MySQL.
Continue readingWhen using FOR XML in SQL Server, we can use the ELEMENTS directive to include a column as an element instead of an attribute. However by default, if a column contains a NULL value, no element is produced for that column in the resulting XML document. This may or may not be what we want, depending on the requirements.
If we want such columns to be included in the XML even when they contain NULL values, all we need to do is include the XSINIL option. This option specifies that any column that has a NULL value automatically gets an element with xsi:nil="true" in the resulting XML.
The alternative is ABSENT, which means columns with NULL values are excluded (this is the default behaviour).
When using FOR XML EXPLICIT in SQL Server, we can use the ELEMENT directive to include a column as an element instead of an attribute. However, this directive doesn’t allow for NULL values. What I mean is that if a column contains a NULL value, no element is produced for that column in the resulting XML document. This may or may not be what we want, depending on the requirements.
If we want such columns to be included in the XML even when they contain NULL values, we can use the ELEMENTXSINIL directive instead of ELEMENT.
Trying to convert a number to a date in SQL Server can be tricky and may not always work. It all depends on the number and what exactly it is that we’re trying to do. That said, here are some scenarios where we can convert a number to a date value.
Continue readingIf you’re getting an error that reads “ERR wrong number of arguments for ‘srandmember’ command” in Redis, it’s probably because you’re calling the SRANDMEMBER command without any arguments.
To fix this issue, make sure you pass the correct number of arguments. At the time of writing, the SRANDMEMBER command requires at least one argument, and accepts an optional second argument.
When creating a table with SQL, we can specify that the table is only to be created if it doesn’t already exist. Doing this prevents any errors from occurring in the event that the table already exists.
Here are some examples of doing this in various RDBMSs.
Continue readingIf you get an error that reads “WRONGTYPE Operation against a key holding the wrong kind of value” when using the ZINTER command in Redis, it’s probably because you’re passing a key with the wrong data type.
To fix this issue, be sure that each key you pass to the ZINTER command is either a set or a sorted set.
Starting with Redis 6.2.0, the ZRANGE command added the REV, BYSCORE, BYLEX and LIMIT options. The addition of the first three options means that the ZRANGE command can now do what the ZREVRANGE, ZRANGEBYSCORE, ZREVRANGEBYSCORE, ZRANGEBYLEX and ZREVRANGEBYLEX commands can do.
As a result, those commands are now deprecated (as of Redis 6.2.0).
Therefore, we should no longer use the ZREVRANGEBYLEX command. Instead, we should use the ZRANGE command with the BYLEX and REV arguments.
If you’re getting an error that reads Argument data type datetime2 is invalid for argument 1 of isdate function, it’s because you’re passing a datetime2 value to the ISDATE() function, but this function doesn’t work with datetime2 values.
To fix this issue, either pass a valid date type or use the work around below to provide similar functionality that works with datetime2 values.
Continue reading