First query execution

First of all, we need to prepare some table for query execution. For example, you can make a simple text-based table as follows:

$ mkdir /home/x/table1
$ cd /home/x/table1
$ cat > data.csv
<CTRL + D>

Apache Tajo™ provides a SQL shell which allows users to interactively submit SQL queries. In order to use this shell, please execute bin/tsql

$ $TAJO_HOME/bin/tsql

In order to load the table we created above, we should think of a schema of the table. Here, we assume the schema as (int, text, float, text).

$ $TAJO_HOME/bin/tsql
tajo> create external table table1 (
      id int,
      name text,
      score float,
      type text)
      using csv with ('text.delimiter'='|') location 'file:/home/x/table1';

To load an external table, you need to use ‘create external table’ statement. In the location clause, you should use the absolute directory path with an appropriate scheme. If the table resides in HDFS, you should use ‘hdfs’ instead of ‘file’.

If you want to know DDL statements in more detail, please see Query Language.

 tajo> \d

``\d`` command shows the list of tables. ::

 tajo> \d table1

 table name: table1
 table path: file:/home/x/table1
 store type: CSV
 number of rows: 0
 volume (bytes): 78 B
 id      INT
 name    TEXT
 score   FLOAT
 type    TEXT

\d [table name] command shows the description of a given table.

Also, you can execute SQL queries as follows:

tajo> select * from table1 where id > 2;
final state: QUERY_SUCCEEDED, init time: 0.069 sec, response time: 0.397 sec
result: file:/tmp/tajo-hadoop/staging/q_1363768615503_0001_000001/RESULT, 3 rows ( 35B)

id,  name,  score,  type
- - - - - - - - - -  - - -
3,  ghi,  3.4,  c
4,  jkl,  4.5,  d
5,  mno,  5.6,  e

tajo> \q

Feel free to enjoy Tajo with SQL standards. If you want to know more explanation for SQL supported by Tajo, please refer SQL Language.