Fix Error 137 “Must declare the scalar variable” in SQL Server

If you’re getting SQL Server error 137 that goes something like “Must declare the scalar variable…“, it’s probably because you’re referring to a variable that hasn’t been declared.

If the variable has been declared, it’s possible you’re referring to it incorrectly in the code.

When we use a variable in SQL Server, we must declare the variable first.

To fix this issue, declare the variable. Also be sure to use the right syntax when using it.

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Fixing Error 1066 When Using the HANDLER Statement in MySQL

If you’re getting MySQL error 1066 which reads something like “1066 (42000): Not unique table/alias: ‘products’” when using the HANDLER statement in MySQL, it could be that you’re trying to open a table that’s already open.

If this is the case, be sure to close the table before trying to open it again. Or simply continue working without opening the table again.

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The 6 SERIAL Data Types in PostgreSQL

The SERIAL data type in PostgreSQL is a pseudo-type used to create an auto-incrementing sequence of integers for a column. It is commonly used for primary keys, as it eliminates the need to manually assign unique identifiers for each new record. PostgreSQL handles this by automatically creating a sequence object that supplies a unique number each time a new row is inserted.

PostgreSQL provides three SERIAL types, each with two options for usage; which effectively equates to six different types. So basically, we have six options to choose from when creating a SERIAL column.

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