When we run an UPDATE statement in SQL, we might not always be interested in which rows or values were updated. But there may be times when we need to examine this data, or log it somewhere like in a separate table.
This is where SQL Server’s OUTPUT clause can help tremendously.
When we have a column with composite data in PostgreSQL, we can access each field by using dot notation. This is true whether we select the data or update it. This means that we can use dot notation to update individual fields within a composite column.
And if we need to update all fields at once, we can use the ROW constructor.
If you’re getting an error that reads “An explicit value for the identity column in table ‘Dogs’ can only be specified when a column list is used and IDENTITY_INSERT is ON” in SQL Server, it appears that you’re trying to insert a value into an IDENTITY column.
Specifically, you’re trying to do that while the IDENTITY_INSERT option is set to OFF.
To fix this issue, either enable IDENTITY_INSERT before inserting the value, or omit the value from your list of values to insert (and let the IDENTITY column do it’s thing).
PostgreSQL provides us with a couple of functions that allow us to pad strings. We can use these functions to put one or more space characters or other characters on either the right side, left side, or both sides of the string.
Continue readingBy default, SQL Server creates indexes automatically when we do things like create certain constraints. We also have the option of creating indexes separately for our own (usually performance related) reasons. Either way, there may be times where we need to check what indexes we have in our database.
In this article, we’ll explore four ways to retrieve information about all indexes in a SQL Server database.
Continue readingIf you’re getting SQL Server error 1909 that reads something like “Cannot use duplicate column names in index. Column name ‘FirstName’ listed more than once“, it appears that you’re trying to create an index, but you’re listing the same column multiple times.
Each column can only be listed once in the index definition.
To fix this issue, make sure each column is listed only once.
Continue readingWhen working with databases (and software in general), string concatenation is the operation of joining character strings end-to-end. For example if we have two words, we can combine them into one.
PostgreSQL provides us with multiple ways to concatenate strings. Below are two functions and one operator that we can use to concatenate strings in PostgreSQL.
Continue readingIf you’re getting an error that reads something like “The objects “employees” and “employees” in the FROM clause have the same exposed names. Use correlation names to distinguish them’” in SQL Server, it could be that you’re trying to do a self-join without assigning table aliases.
When doing self-joins, we need to provide aliases for the tables so that SQL Server can distinguish between each instance.
To fix this issue, be sure to use unique table aliases in your query.
Continue readingCommon Table Expressions (CTEs) are a nifty SQL feature that allow us to define a temporary result set, which can then be used in subsequent queries, including DELETE statements. In the context of removing duplicate data, a CTE can be helpful when we want to identify and remove only the duplicated rows, keeping one version of each unique record.
Let’s go through a step-by-step example of using a CTE with a DELETE statement to remove duplicate data.
If you’re getting an error that reads “Create View or Function failed because no column name was specified…” in SQL Server, perhaps you’re using a function or an arithmetic expression in the SELECT list, but you haven’t provided a name for the column.
As the error message alludes to, you need to provide a column name when doing stuff like that.
Continue reading