You may have seen the term “RID lookup” when reading about heap tables, or perhaps when viewing the query plan for a query against a heap in SQL Server.
But what exactly is a RID lookup? And what exactly is a RID?
Let’s find out.
Continue readingTag: mssql
Fix “Incorrect syntax near the keyword ‘Order'” in SQL Server (Error 156)
If you’re getting an error in SQL Server that reads “Incorrect syntax near the keyword ‘Order’“, it could be because you’re using the word Order (or another reserved keyword) in your SQL code.
The 156 error itself merely indicates a syntax error, so there could be a multitude of reasons you might be getting this error. But when it refers to the keyword 'Order', this could suggest that you’re trying to use the word Order as an identifier (such as a column name, table name, etc).
Understanding the ON UPDATE SET NULL Option for Foreign Keys in SQL Server
In SQL Server (and relational databases in general), a foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table.
This relationship is a cornerstone of relational database design, ensuring referential integrity between the related tables. When designing databases, it’s crucial to understand how changes to primary keys in parent tables can affect the foreign keys in child tables.
One of the various options available in SQL Server for handling such changes is the ON UPDATE SET NULL action.
Fix Error 156 “Incorrect syntax near the keyword ‘ON'” When Using DROP_EXISTING in SQL Server
If you’re getting an error that reads something like “Incorrect syntax near the keyword ‘ON’“, it appears that you’re trying to recreate an existing index, but you’re using the wrong syntax for the DROP_EXISTING argument.
The same error occurs when using the wrong syntax to set DROP_EXISTING to OFF; “Incorrect syntax near the keyword ‘OFF’“.
Either way, to fix this issue, be sure to use the right syntax.
Continue readingFix Error 4145 “An expression of non-boolean type specified in a context where a condition is expected” in SQL Server
If you’re getting SQL Server error 4145 that goes something like “An expression of non-boolean type specified in a context where a condition is expected…“, it’s probably because you’re using a boolean-like syntax in the wrong context.
This error occurs when a non-boolean expression is used in a context where a condition (i.e., something that evaluates to true or false) is expected. This often happens in IF statements, CASE expressions, or WHERE clauses when a value that isn’t a boolean is mistakenly used as a condition.
Even when we do use a boolean value, we can still get this error if we use it in the wrong context.
Continue readingFix Error 107 “The column prefix … does not match with a table name or alias name used in the query” in SQL Server
If you’re getting SQL Server error 107 that goes something like “The column prefix ‘e’ does not match with a table name or alias name used in the query“, look at your column prefix.
This error occurs when we use the asterisk wildcard (*) that’s incorrectly qualified with a column prefix. The prefix, if provided, must match a table name or alias name. If you’re using a table alias, then you must use that instead of the table name.
Fix Error 547 “The DELETE statement conflicted with the REFERENCE constraint…” in SQL Server
If you’re getting SQL Server error 547 that reads something like “The DELETE statement conflicted with the REFERENCE constraint “FK_Projects_DepartmentID”. The conflict occurred in database “test”, table “dbo.Projects”, column ‘DepartmentID’“, you’re probably trying to delete data from a parent table of a foreign key relationship.
Continue readingUnderstanding the ON DELETE SET DEFAULT Option in SQL Server
In SQL Server, foreign keys are essential for maintaining referential integrity between tables. When setting up a foreign key, we have various options for handling actions when the referenced data is deleted. One of these options is ON DELETE SET DEFAULT.
This feature can be particularly useful in scenarios where it’s important to maintain the relationship while ensuring that the foreign key column doesn’t end up with invalid or null values.
Continue readingFix Error 1785 “Introducing FOREIGN KEY constraint … may cause cycles or multiple cascade paths” in SQL Server
If you’re getting SQL Server error 1785 that reads something like “Introducing FOREIGN KEY constraint ‘FK__Name’ on table ‘Department’ may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints“, it’s probably because you’ve specified the CASCADE option when trying to create a foreign key with a circular reference, or one that has multiple cascade paths (perhaps your child table has multiple foreign keys to the same primary key on the parent table).
What is Domain Integrity?
Domain integrity is an important concept in relational database management that ensures the accuracy, validity, and consistency of data within a database. It refers to the enforcement of rules and constraints that ensure data entered into a database adheres to a predefined set of acceptable values. This helps maintain the quality of data and prevents the entry of erroneous, incomplete, or invalid data into the system.
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