A SELECT statement can consist of the following basic clauses.

• SELECT
• INTO
• FROM
• JOIN
• WHERE
• GROUP BY
• HAVING
• UNION
• ORDER BY
• LIMIT

SELECT Syntax

The following syntax diagram outlines the syntax supported by the FHIR adapter:

SELECT {
  [ TOP <numeric_literal> | DISTINCT ]
  { 
    * 
    | { 
        <expression> [ [ AS ] <column_reference> ] 
        | { <table_name> | <correlation_name> } .* 
      } [ , ... ] 
  }
  { 
    FROM <table_reference> [ [ AS ] <identifier> ] 
  } [ , ... ]
  [ 
    JOIN <table_reference> [ ON <search_condition> ] [ [ AS ] <identifier> ] 
  ] [ ... ] 
  [ WHERE <search_condition> ]
  [ GROUP BY <column_reference> [ , ... ]
  [ HAVING <search_condition> ]
  [ UNION  [ ALL ] <select_statement> ]
  [ 
    ORDER BY 
    <column_reference> [ ASC | DESC ] [ NULLS FIRST | NULLS LAST ]
  ]
  [
    LIMIT <expression>
    [ 
      { OFFSET | , }
      <expression> 
    ]
  ] 
}

  <expression> ::=
    | <column_reference>
    | @ <parameter> 
    | ?
    | COUNT( * | { [ DISTINCT ] <expression> } )
    | { AVG | MAX | MIN | SUM | COUNT } ( <expression> ) 
    | NULLIF ( <expression> , <expression> ) 
    | COALESCE ( <expression> , ... ) 
    | CASE <expression>
        WHEN { <expression> | <search_condition> } THEN { <expression> | NULL } [ ... ]
    [ ELSE { <expression> | NULL } ]
      END 
    | <literal>
    | <sql_function> 

  <search_condition> ::= 
    {
      <expression> { = | AND | > | < | >= | <= | LIKE | IN } [ <expression> ]
    } [ { AND | OR } ... ]

Examples

1. Return all columns:
   

   SELECT * FROM Patient

2. Rename a column:
   

   SELECT "[address-city]" AS MY_[address-city] FROM Patient

3. Cast a column's data as a different data type:
   

   SELECT CAST(AnnualRevenue AS VARCHAR) AS Str_AnnualRevenue FROM Patient

4. Search data:
   

   SELECT * FROM Patient WHERE [name-use] = 'Bob'

5. The FHIR APIs support the following operators in the WHERE clause: =, AND, >, <, >=, <=, LIKE, IN.
   

   SELECT * FROM Patient WHERE [name-use] = 'Bob';

6. Return the number of items matching the query criteria:
   

   SELECT COUNT(*) AS MyCount FROM Patient 

7. Return the number of unique items matching the query criteria:
   

   SELECT COUNT(DISTINCT [address-city]) FROM Patient 

8. Return the unique items matching the query criteria:
   

   SELECT DISTINCT [address-city] FROM Patient 

9. Sort a result set in ascending order:
   

   SELECT Id, [address-city] FROM Patient  ORDER BY [address-city] ASC

Aggregate Functions

For SELECT examples using aggregate functions, see Aggregate Functions.

JOIN Queries

See JOIN Queries for SELECT query examples using JOINs.

Date Literal Functions

Date Literal Functions contains SELECT examples with date literal functions.

Window Functions

See Window Functions for SELECT examples containing window functions.

Table-Valued Functions

See Table-Valued Functions for SELECT examples with table-valued functions.