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The following page has been changed by InchulSong: http://wiki.apache.org/lucene-hadoop/Hbase/HbaseShell/HQL The comment on the change is: some refinements on the HQL syntax ------------------------------------------------------------------------------ == Hbase Query Language (HQL) Introduction == HQL is an SQL-like query language for Hbase. You can use it to query and modify tables in Hbase. HQL is not intended to fully support the SQL syntax and semantics. - HQL, instead, is developed to make it easy to manipulate tables in Hbase through the Hbase Shell command line, + HQL, instead, is developed to help easy manipulation of tables in Hbase through the Hbase Shell command line without using programming APIs. - without using programming APIs. We borrowed the syntax definition style from MySQL. + The issue [https://issues.apache.org/jira/browse/HADOOP-1720 HADOOP-1720] is adding HQL support to the Hbase Shell. + ''Thanks to Edward Yoon for his initial idea of HQL, and to Stack for his suggestions. Any suggestions for HQL in this wiki page, or to [[MailTo(icsong AT SPAMFREE gmail DOT com)]]'' - ''Thanks to Edward Yoon for his initial idea of HQL, and to Stack for his valuable suggestions.'' - - ''Any suggestions for HQL to [[MailTo(icsong AT SPAMFREE gmail DOT com)]], or in this wiki page'' == Data Definition Statements == === CREATE TABLE Syntax === - CREATE TABLE enables you to create a new table and set various options for each column family. - {{{ CREATE TABLE table_name ( - column_family_name [MAX_VERSIONS=n], - ... - ) - }}} - - * MAX_VERSIONS is for the management of versioned data. MAX_VERSIONS makes a table keep only the recent n versions in a cell under a column family. Its default value is 1, i.e., if MAX_VERSIONS is not specified, Hbase keeps only the latest version of value in a cell. - - {{{ - CREATE TABLE table_name ( - column_family_spec, + column_family_spec + [, column_family_spec] ... ) colum_family_spec: - column_family_name [MAX_VERSIONS=n] [LENGTH=n] - [COMPRESSION=no | block | record] [IN_MEMORY] - [BLOOMFILTER=bloom | counting | retouched] + column_family_name + [MAX_VERSIONS=n] + [MAX_LENGTH=n] + [COMPRESSION=NONE|BLOCK|RECORD] + [IN_MEMORY] + [BLOOMFILTER=NONE|BLOOM|COUNTING|RETOUCHED] }}} + CREATE TABLE enables you to create a new table with various options for each column family. + + * MAX_VERSIONS makes a table keep only the recent n versions in a cell. Its default value is 3, i.e., only the most recent 3 versions of values are stored in a cell. + * MAX_LENGTH specifies the maximum size of a column value. By default, the maximum size is unlimited. It is limited only by Integer.MAX_VALUE. + * COMPRESSION specifies which compression technique to use for the column family. By default, Hbase does not compress any data. + * IN_MEMORY specifies whether to keep the values in the column family in-memory, or not. By default, values are not kept in-memory. + * BLOOMFILTER specifies which bloom filter to use for the column family. By default, none of the bloom filters is used. - * Full version of CREATE TABLE. See [http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Nightly/javadoc/org/apache/hadoop/hbase/HColumnDescriptor.html HColumnDescriptor API] for more information. + * See [http://lucene.zones.apache.org:8080/hudson/job/Hadoop-Nightly/javadoc/org/apache/hadoop/hbase/HColumnDescriptor.html HColumnDescriptor API] for more information. === DROP TABLE Syntax === - DROP TABLE removes one or more tables. - {{{ DROP TABLE table_name [, table_name] ... }}} + DROP TABLE removes one or more tables. + === ALTER TABLE Syntax === - ALTER TABLE enables you to change the structure of an existing table. You can - add, delete, and change column families. - {{{ ALTER TABLE table_name alter_spec [, alter_spec] ... @@ -65, +60 @@ | CHANGE column_family_name column_family_spec }}} + ALTER TABLE changes the structure of an existing table. You can + add, delete, or change column families. + == Data Manipulation Statements == === SELECT Syntax === - SELECT enables you to retrieve a subset of data in a table. - {{{ - SELECT { column_name, ... | * } + SELECT { column_name [, column_name] ... | * } FROM table_name [WHERE row = 'row-key' | STARTING FROM 'row-key'] [NUM_VERSIONS = version_count] [TIMESTAMP 'timestamp'] [LIMIT = row_count] - [INTO FILE 'file_name' options] + [INTO FILE 'file_name'] column_name: + column_family_name - column_family_name:column_label_name + | column_family_name:column_label_name - | column_family_name: - - options: - FIELDS DELIMITED BY 'string' [ENCLOSED BY 'char'] }}} - * You should quote column_name with single quotes if column_name has spaces in it. + SELECT retrieves a subset of data from the specified table. + + * A column_name with spaces in it should be single-quoted. - * If you specify only column_family_name part for a column, you get values from all the column_label_names in the column_family_name. - * STARTING FROM returns all the rows starting from 'row-key'. * NUM_VERSIONS retrieves only the recent n versions of values in a cell. @@ -98, +91 @@ * LIMIT limits the number of rows to be returned. + * INTO FILE outputs the returned rows into the specified file. For SELECT INTO another table, see INSERT INTO SELECT below. - * INTO FILE outputs the returned rows into a specified file. options specifies how to delimit each field in the file. For SELECT INTO another table, see INSERT below. - - ''~- "add some row filtering here, i.g., regex match or upper limit on rows returned." -~'' by Stack. See issue [https://issues.apache.org/jira/browse/HADOOP-1611 HADOOP-1611]. === INSERT Syntax === - INSERT inserts a set of values into a table. - {{{ INSERT INTO table_name (colmn_name, ...) VALUES ('value', ...) @@ -112, +101 @@ [TIMESTAMP 'timestamp'] }}} - * If a specified column already exists, the specified value for the column is stored as a new version. + INSERT inserts a set of values into a table. + * If the specified column already exists, the new value is stored as a new version. + - * If TIMESTAMP is not specified, the current time is used as the value of the timestamp key. + * If TIMESTAMP is not specified for the value, the current time is used as its timestamp. {{{ - INSERT INTO table_name (column_name, ...) + INSERT INTO table_name (colmn_name, ...) [TIMESTAMP 'timestamp'] SELECT ... }}} @@ -125, +116 @@ * TIMESTAMP inserts the rows selected by SELECT ... with the specified timestamp === DELETE Syntax === - DELETE removes a subset of data from a table. - {{{ - DELETE { column_name, [, column_name] ... | * } + DELETE { column_name, [, column_name] ... | *} FROM table_name WHERE row = 'row-key' }}} + DELETE removes a subset of data from a table. + === LOAD FROM FILE Syntax === - LOAD FROM FILE reads rows from a file and inserts these rows into a table. - {{{ LOAD FROM FILE 'file_name' INTO TABLE table_name [options] }}} - * LOAD FROM FILE is complement of SELECT INTO FILE. + LOAD FROM FILE reads rows from the specified file and inserts these rows into the specified table. LOAD FROM FILE is complement of SELECT INTO FILE. + === SOURCE Syntax === + {{{ + SOURCE 'file_name' + }}} + + SOURCE reads HQL statements from the specified file and executes them. + + == Miscellaneous Statements == + {{{ + SHOW TABLES + }}} + + SHOW TABLES shows all available tables, including disabled tables. For disabled tables, + it shows that they are disabled. + + {{{ + DESCRIBE table_name + }}} + + DESCRIBE shows the structure of the specified table such as the table's column families, compression technique being used, and so on. + + {{{ + ENABLE | DISABLE table_name + }}} + + ENABLE (DISABLE) enables (disables) the specified table. + + == Transaction-Related Statements == === START TRANSACTION, COMMIT, and ROLLBACK Syntax === - You can group togather a sequence of data manipulation statements in a single-row transaction. - {{{ START TRANSACTION ON 'row-key' OF table_name | BEGIN ON 'row-key' OF table_name COMMIT ['timestamp'] ROLLBACK }}} - * The START TRANSACTION and BEGIN statements begin a new single-row transaction under a 'row-key' of table_name. + You can group together a sequence of data manipulation statements in a single-row transaction. - * COMMIT commits the current transaction, making its changes permanent. If timestamp is specified on commit, all the modifications under a single-row transaction are stored with the specified timestamp. If not, they are stored with the current time. + The START TRANSACTION and BEGIN statements begin a new single-row transaction under the specified 'row-key' of table_name. - * ROLLBACK rolls back the current transaction, canceling its changes. + COMMIT commits the current transaction, making its changes permanent. If timestamp is specified on commit, all the modifications under the single-row transaction are stored with the specified timestamp. If not, they are stored with the current time as their timestamps. + ROLLBACK rolls back the current transaction, canceling its changes. + - * By default, for every statement execution that updates a table, Hbase immediately stores the update on disk. + By default, for every statement execution that updates a table, Hbase immediately stores the update on disk. ''~- TRANSACTION on a row-level only -- and this is all you could guarantee in HBase -- may be a bit-over-the-top and require more effort than its worth. How about implementing this one last, if it is needed at all? -- St.Ack-~'' - == Other Statements == - SHOW TABLES shows all available tables. - - {{{ - SHOW TABLES - }}} - - DESCRIBE shows the structure of a table, including available column families and their settings such as compression options, bloom filters, and so on. - - {{{ - DESCRIBE table_name - }}} - - {{{ - ENABLE | DISABLE table_name - }}} -
