Information schema and Primary Keys - sql-server

Question

How do I just print out a 'primary key' for the column with the primary key?
I get 'primary key' for all the columns if the table has a primary key, instead of the one column with the primary key and the other columns as blank in keyType.
SELECT c.TABLE_NAME,
c.COLUMN_NAME,
c.DATA_TYPE,
c.Column_default,
c.character_maximum_length,
c.numeric_precision,
c.is_nullable,
CASE
WHEN u.CONSTRAINT_TYPE = 'PRIMARY KEY' THEN 'primary key'
ELSE ''
END AS KeyType
FROM INFORMATION_SCHEMA.COLUMNS as c
LEFT JOIN information_schema.table_constraints as u ON c.table_name = u.table_name
ORDER BY table_name

Answer 1

SELECT c.TABLE_NAME, c.COLUMN_NAME,c.DATA_TYPE, c.Column_default, c.character_maximum_length, c.numeric_precision, c.is_nullable
,CASE WHEN pk.COLUMN_NAME IS NOT NULL THEN 'PRIMARY KEY' ELSE '' END AS KeyType
FROM INFORMATION_SCHEMA.COLUMNS c
LEFT JOIN (
SELECT ku.TABLE_CATALOG,ku.TABLE_SCHEMA,ku.TABLE_NAME,ku.COLUMN_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS tc
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS ku
ON tc.CONSTRAINT_TYPE = 'PRIMARY KEY'
AND tc.CONSTRAINT_NAME = ku.CONSTRAINT_NAME
) pk
ON c.TABLE_CATALOG = pk.TABLE_CATALOG
AND c.TABLE_SCHEMA = pk.TABLE_SCHEMA
AND c.TABLE_NAME = pk.TABLE_NAME
AND c.COLUMN_NAME = pk.COLUMN_NAME
ORDER BY c.TABLE_SCHEMA,c.TABLE_NAME, c.ORDINAL_POSITION

Answer 2

As an addition, consider looking at:
sp_helptext N'sp_help'
Sometimes learning from the MS team is a great thing. :-)

Answer 3

a very small add to the first answer. It's possible to view in same time the MS_Description (or other extend properties)
SELECT c.TABLE_NAME, c.COLUMN_NAME,c.DATA_TYPE, c.Column_default, c.character_maximum_length, c.numeric_precision, c.is_nullable
,CASE WHEN pk.COLUMN_NAME IS NOT NULL THEN 'PRIMARY KEY' ELSE '' END AS KeyType, c.ORDINAL_POSITION
,convert(varchar(8000), ex.value) as coln
FROM INFORMATION_SCHEMA.COLUMNS c
LEFT JOIN (
SELECT ku.TABLE_CATALOG,ku.TABLE_SCHEMA,ku.TABLE_NAME,ku.COLUMN_NAME
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS tc
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS ku
ON tc.CONSTRAINT_TYPE = 'PRIMARY KEY'
AND tc.CONSTRAINT_NAME = ku.CONSTRAINT_NAME
) pk
ON c.TABLE_CATALOG = pk.TABLE_CATALOG
AND c.TABLE_SCHEMA = pk.TABLE_SCHEMA
AND c.TABLE_NAME = pk.TABLE_NAME
AND c.COLUMN_NAME = pk.COLUMN_NAME
outer apply ::fn_listextendedproperty('MS_Description', 'schema', 'dbo', 'table', c.TABLE_NAME, 'column', c.COLUMN_NAME) ex
ORDER BY c.TABLE_SCHEMA,c.TABLE_NAME, c.ORDINAL_POSITION

Answer 4

I've found this code below to be the simplest method to find the primary key for a table. It only requires a left outer join between the information_schema.columns table and the information_schema.key_column_usage table.
Select
col.column_name,
col.data_type,
col.ordinal_position,
col.is_nullable,
case when ky.COLUMN_NAME is null then 0 else 1 end as primary_key_flag
from <your-catalog>.Information_Schema.columns col
left outer join <your-catalog>.INFORMATION_SCHEMA.KEY_COLUMN_USAGE ky
on ky.COLUMN_NAME = col.COLUMN_NAME and ky.TABLE_NAME = col.TABLE_NAME
and ky.TABLE_CATALOG = col.TABLE_CATALOG and ky.table_name = col.table_name
where
col.TABLE_NAME = '<your-table-name>'
and col.table_catalog = '<your-catalog>';
Note: This code was built using SQL Server 2017 Express (14.0.1000) and after I created the primary key, I was able to see those values in the KEY_COLUMN_USAGE table. I also saw a record in the CONSTRAINT_TABLE_USAGE which identified the constraint_name, but I didn't find that to be a requirement in order to get the join into which revealed the primary key.
Final note: I'm just getting back into SQL server on a personal project after nearly a decade away from the DB (using MySQL), and so I'm nowhere near an expert on the subject.