Altering column size in SQL Server

Scrutinize before you resize

Best practices for data integrity

Check on the existing data in your column before changing its size or type, ensuring in the new type or size all the data will fit in comfortably. When it comes to altering to a type like NUMERIC(22, 5), assure that chosen precision and scale are compatible with your existing data. Because we all want our data to be Peter Parker (Integrity man), not Dr Octopus (functional disruption).

Nullability of the columns: nullable or not?

A column's nullability should be treated like rockstar concert tickets, you do check if it's available, right? So, for nullable columns, include NULL or NOT NULL in your ALTER COLUMN statement but only after verifying the existing nullability status with our good friend COLUMNPROPERTY.

IF COLUMNPROPERTY(OBJECT_ID('dbo.tbl'), 'col', 'AllowsNull') = 1
    -- Null you say? Sure, we shall keep it null then
    ALTER TABLE dbo.tbl ALTER COLUMN col NUMERIC(22, 5) NULL; 
ELSE
    -- If not, Not Null it remains
    ALTER TABLE dbo.tbl ALTER COLUMN col NUMERIC(22, 5) NOT NULL;
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Downtime: Minimize it

Traditional ALTER TABLE may cause cricket sounds in your application due to table lock semantics. For bigger tables or heavy-transaction systems, consider downtime minimizing techniques like bats scheduling (alter schema changes during maintenance windows) or making use of Dr. Strange Time stone (also known as "How To Enlarge Your Columns With No Downtime" by spaghettidba).

Row compression to the rescue

Thinking to use row compression before altering the type? Boy oh boy, good idea! It can prevent your data from unneeded rewrite hassle:

ALTER TABLE dbo.tbl REBUILD WITH (DATA_COMPRESSION = ROW);
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Unraveling the NUMERIC preset

The NUMERIC(precision, scale) data type is your comrade when it comes to precise precision in numerical data. Precision counts total digits whereas scale counts digits after decimal.

Understanding the syntactical subtleties

SQL syntax is eccentric, honestly. Maybe it's the way it carries a commanding tone, or it's all the hats it wears — data manipulator, query commander, type caster - jack of all trades really. Mislay a NULL and you got unrest, scramble up type specification and you may encounter errors or witness undisciplined behaviour. Always crosscheck your statements over SQL Server Documentation.

Advanced Optimizations: Ready, Set, Go

Carving out a high-performance or large database, you'd fancy batch alterations or online indexing operations. This could ensure database availability, similar to how superheroes ensure world peace.