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 Apache Impala adapter:

SELECT {
  [ TOP <numeric_literal> | DISTINCT ]
  { 
    * 
    | { 
        <expression> [ [ AS ] <column_reference> ] 
        | { <table_name> | <correlation_name> } .* 
      } [ , ... ] 
  }
  { 
    FROM <table_reference> [ [ AS ] <identifier> ] 
  } [ , ... ]
  [ [ 
      INNER | { { LEFT | RIGHT | FULL  } [ OUTER ] }  
    ] 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> 
    ]
  ] 
} | SCOPE_IDENTITY() 

  <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> { = | > | < | >= | <= | <> | != | LIKE | IN | NOT IN | AND | OR } [ <expression> ]
    } [ { AND | OR } ... ]

Examples

1. Return all columns:
   

   SELECT * FROM [CData].[Default].Customers

2. Rename a column:
   

   SELECT "CompanyName" AS MY_CompanyName FROM [CData].[Default].Customers

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

   SELECT CAST(Balance AS VARCHAR) AS Str_Balance FROM [CData].[Default].Customers

4. Search data:
   

   SELECT * FROM [CData].[Default].Customers WHERE Country = 'US'

5. The Apache Impala APIs support the following operators in the WHERE clause: =, >, <, >=, <=, <>, !=, LIKE, IN, NOT IN, AND, OR.
   

   SELECT * FROM [CData].[Default].Customers WHERE Country = 'US';

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

   SELECT COUNT(*) AS MyCount FROM [CData].[Default].Customers 

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

   SELECT COUNT(DISTINCT CompanyName) FROM [CData].[Default].Customers 

8. Return the unique items matching the query criteria:
   

   SELECT DISTINCT CompanyName FROM [CData].[Default].Customers 

9. Sort a result set in ascending order:
   

   SELECT City, CompanyName FROM [CData].[Default].Customers  ORDER BY CompanyName 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.

Projection Functions

See Projection Functions for SELECT examples with projection functions.

Predicate Functions

For SELECT examples using predicate functions, see Predicate Functions.