Quotation mark incorrect when using crosstab() in PostgreSQL

Question

I have a table t1 as below:

create table t1 (
  person_id int,
  item_name varchar(30),
  item_value varchar(100)
);

There are five records in this table:

person_id | item_name | item_value
   1        'NAME'      'john'
   1        'GENDER'    'M'
   1        'DOB'       '1970/02/01'
   1        'M_PHONE'   '1234567890'
   1        'ADDRESS'   'Some Addresses unknown'

Now I want to use crosstab function to extract NAME, GENDER data, so I write a SQL as:

select * from crosstab(
  'select person_id, item_name, item_value from t1 
   where person_id=1 and item_name in ('NAME', 'GENDER') ') 
as virtual_table (person_id int, NAME varchar, GENDER varchar)

My problem is, as you see the SQL in crosstab() contains condition of item_name, which will cause the quotation marks to be incorrect. How do I solve the problem?

Answer 1

To avoid any confusion about how to escape single quotes and generally simplify the syntax, use dollar-quoting for the query string:

SELECT *
FROM   crosstab(
   $$
   SELECT person_id, item_name, item_value
   FROM   t1 
   WHERE  person_id = 1
   AND    item_name IN ('NAME', 'GENDER')
   $$
   ) AS virtual_table (person_id int, name varchar, gender varchar);

See:

• Insert text with single quotes in PostgreSQL

And you should add ORDER BY to your query string. I quote the manual for the tablefunc module:

In practice the SQL query should always specify ORDER BY 1,2 to ensure that the input rows are properly ordered, that is, values with the same row_name are brought together and correctly ordered within the row. Notice that crosstab itself does not pay any attention to the second column of the query result; it's just there to be ordered by, to control the order in which the third-column values appear across the page.

See:

• PostgreSQL Crosstab Query

Answer 2

Double your single quotes to escape them:

select * from crosstab(
  'select person_id, item_name, item_value from t1 
   where person_id=1 and item_name in (''NAME'', ''GENDER'') ') 
as virtual_table (person_id int, NAME varchar, GENDER varchar)