Selecting random row and or random sample from SQL and previous format use like so using the ORDER BY with the random Unique Identifier for each row randomly arranges the rows and then

SELECT TOP 10 PERCENT *
FROM MyTable
ORDER BY NEWID()

Now use tablesample

<tablesample_clause> ::=  
    TABLESAMPLE [SYSTEM] ( sample_number [ PERCENT | ROWS ] )   
        [ REPEATABLE ( repeat_seed ) ]

Which should be like this

SELECT *
FROM MyTable
TABLESAMPLE (10 PERCENT)

In Postgres the syntax for tablesample is slightly different

Default

SELECT * 
FROM MyTable TABLESAMPLE SYSTEM (10);

Bernoulli sampling

SELECT *
FROM MyTable TABLESAMPLE BERNOULLI (10);