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dev:sql:statements:partition:home [2010/07/02 07:28] tdo |
dev:sql:statements:partition:home [2016/06/28 22:38] (current) |
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| - | + | ====== Omnidex SQL: PARTITION ====== | |
| - | ====== Omnidex SQL: PARTITION table ====== | + | {{page>:sql_bar&nofooter&noeditbtn}} |
| ===== Description ===== | ===== Description ===== | ||
| - | Partitions a table into multiple sub partitions which can be useful when setting up an Omnidex grid. | + | The PARTITION statement reads a table and splits it into multiple sub partitions which can be useful when setting up an Omnidex grid. |
| ===== Syntax ===== | ===== Syntax ===== | ||
| <code> | <code> | ||
| - | PARTITION table | + | PARTITION table_spec |
| [INTO n] | [INTO n] | ||
| - | [BY <column | expression>] | + | [BY <column_spec | expression>] |
| [IN path] | [IN path] | ||
| - | [ON [INSTANCE] instance] | + | [ON [INSTANCE] instance_no] |
| [WITH options] | [WITH options] | ||
| </code> | </code> | ||
| + | ===== Discussion ===== | ||
| + | |||
| + | The output of the PARTITION statement is multiple files that are named as follows: table_name_<distinct_value>.dat. | ||
| - | ===== Discussion ===== | + | |
| + | ===== Examples ===== | ||
| + | ==== Partition by Column ==== | ||
| + | This example will partition a table into multiple sub tables for each state. Note that the filename suffix is the distinct state value. | ||
| + | <code> | ||
| + | > partition households by state ; | ||
| + | Partitioned 1,909 rows from HOUSEHOLDS into 52 partitions | ||
| + | > dir | ||
| + | HOUSEHOLDS_AK.dat | ||
| + | HOUSEHOLDS_AL.dat | ||
| + | HOUSEHOLDS_AR.dat | ||
| + | HOUSEHOLDS_AZ.dat | ||
| + | HOUSEHOLDS_CA.dat | ||
| + | HOUSEHOLDS_CO.dat | ||
| + | HOUSEHOLDS_CT.dat | ||
| + | HOUSEHOLDS_DC.dat | ||
| + | HOUSEHOLDS_DE.dat | ||
| + | HOUSEHOLDS_FL.dat | ||
| + | HOUSEHOLDS_GA.dat | ||
| + | HOUSEHOLDS_HI.dat | ||
| + | HOUSEHOLDS_IA.dat | ||
| + | HOUSEHOLDS_ID.dat | ||
| + | HOUSEHOLDS_IL.dat | ||
| + | HOUSEHOLDS_IN.dat | ||
| + | HOUSEHOLDS_KS.dat | ||
| + | HOUSEHOLDS_KY.dat | ||
| + | HOUSEHOLDS_LA.dat | ||
| + | … | ||
| + | </code> | ||
| + | ==== Partition with criteria and CASE ==== | ||
| The partition statement is used with criteria to split a table into multiple components. | The partition statement is used with criteria to split a table into multiple components. | ||
| The SQL CASE syntax can be used to specify the suffix used when the PARTITION statement creates the component files. | The SQL CASE syntax can be used to specify the suffix used when the PARTITION statement creates the component files. | ||
| <code> | <code> | ||
| - | > partition companies by "case when state in ('CA','CO','TX') then '01' when state in ('NY','FL','WA') then '02' else '03' end" ; | + | > partition companies by |
| + | "case when state in ('CA','CO','TX') then '01' | ||
| + | when state in ('NY','FL','WA') then '02' | ||
| + | else '03' end" ; | ||
| Partitioned 31,548 rows from COMPANIES into 3 partitions | Partitioned 31,548 rows from COMPANIES into 3 partitions | ||
| </code> | </code> | ||
| - | |||
| - | |||
| - | ===== Examples ===== | ||
| - | |||
| - | ==== Simple ==== | ||
| - | |||
| - | ==== 2nd example ==== | ||
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