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| - | ~~NOTOC~~ | ||
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| - | ====== Administration: Omnidex Indexing ====== | ||
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| - | ===== Omnidex Text ===== | ||
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| - | [[admin:indexing:text:home|Overview]] | | ||
| - | **[[admin:indexing:text:clob|Textual Datatypes]]** | | ||
| - | [[admin:indexing:text:retrieve|External Files]] | | ||
| - | [[admin:indexing:text:proximity|Proximity Searches]] | | ||
| - | [[admin:indexing:text:results|Displaying Results]] | | ||
| - | [[admin:indexing:text:relevancy|Relevancy]] | ||
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| - | ---- | ||
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| - | ==== Textual Datatypes ==== | ||
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| - | Databases store text in character columns or in variable character columns (often called VARCHAR columns). These datatypes are good for storing smaller amounts of text, such as names, addresses and short descriptions. These datatypes are often limited in size, though. For larger amounts of text, a database may employ special datatypes designed specifically for this purpose. As examples, Oracle provides a CLOB (Character Large Object) datatype and SQL Server provides a TEXT datatype. These datatypes can often store up to 2-4 gigabytes of text. | ||
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| - | ^ Datatype ^ Description ^ | ||
| - | |CHARACTER|Space-padded data up to 4,095 bytes.| | ||
| - | |C STRING|Null-terminated data up to 64MB. If indexed with Omnidex, the extracted text from this column may be up to 16MB.| | ||
| - | |VARCHAR|Non-terminated and non-padded data up to 4,095 bytes. This datatype may contain embedded null characters since it is not null-terminated; however, it should not be used to store binary data. Use of this datatype requires use of oadescribe and oabind so that the data_lengths variables can be used. This allows applications to know the length of the data in this column for each row returned.\\ \\ This datatype is not appropriate for fixed length Flatfiles since the data length cannot be stored. Flatfiles should use CHARACTER, C STRING or OMNIDEX VARCHAR datatypes.| | ||
| - | |CLOB|Non-terminated and non-padded data up to 64MB. If indexed with Omnidex, the extracted text from this column may be up to 16MB. This datatype may contain embedded null characters since it is not null-terminated; however, it should not be used to store binary data. Use of this datatype requires use of oadescribe and oabind so that the data_lengths variables can be used. This allows applications to know the length of the data in this column for each row returned.\\ \\ The handling of CLOB data may be more expensive than the handling of CHARACTER, C STRING and VARCHAR data. It is better to use those datatypes if their size limitations will not be exceeded.\\ \\ This datatype is not appropriate for fixed length Flatfiles since the data length cannot be stored. Flatfiles should use CHARACTER, C STRING, OMNIDEX VARCHAR or OMNIDEX CLOB datatypes.| | ||
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| - | The textual datatypes have different characteristics and have different restrictions within Omnidex SQL. The following table shows the capabilities of each datatype. | ||
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| - | ^Characteristics ^ CHARACTER ^ C STRING ^ VARCHAR ^ CLOB ^ | ||
| - | |\\ **Datatype Characteristics** ||||| | ||
| - | |Character data allowed | Yes | Yes | Yes | Yes | | ||
| - | |Binary data allowed | No | No | No | No | | ||
| - | |Embedded nulls allowed | No | No | Yes | Yes | | ||
| - | |Null-terminated | No | Yes | No | No | | ||
| - | |Data_lengths required | No | No | Yes | Yes | | ||
| - | |Max size | 4,095 | 64mb | 4,095 | 64mb | | ||
| - | |\\ **Usage Characteristics** ||||| | ||
| - | |Select item of simple query | Yes | Yes | Yes | Yes | | ||
| - | |Select item of outer query | Yes | Yes | Yes | Yes | | ||
| - | |Select item of nested query | Yes | Yes | Yes | No | | ||
| - | |Select item of INSERT | Yes | Yes | Yes | No | | ||
| - | |Select item of set operation | Yes | Yes | Yes | Yes | | ||
| - | |Table joins | Yes | Yes | Yes | No | | ||
| - | |WHERE clause | Yes | Yes | Yes | Limited <sup>1</sup> | | ||
| - | |GROUP BY clause | Yes | Yes | Yes | No | | ||
| - | |ORDER BY clause | Yes | Yes | Yes | No | | ||
| - | |HAVING clause | Yes | Yes | Yes | No | | ||
| - | |SELECT INTO clause | Yes | Yes | Yes | No | | ||
| - | |Aggregate functions | Yes | Yes | Yes | No | | ||
| - | |SQL Functions | Yes | Yes | Yes | Limited <sup>2</sup> | | ||
| - | |\\ **Update Characteristics** ||||| | ||
| - | |Inserts, updates and deletes | Yes | Yes | Yes | No | | ||
| - | |--------------------------------------------------------------------------|----------------|----------------|----------------|----------------| | ||
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| - | <sup>1. Limited to use of LIKE, $CONTAINS and IS NULL operators.</sup>\\ | ||
| - | <sup>2.See individual functions for compatibility with CLOB datatype.</sup> | ||
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| - | ===== ===== | ||
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| - | **[[admin:indexing:text:home|Prev]]** | | ||
| - | **[[admin:indexing:text:retrieve|Next]]** | ||
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| - | ====== Additional Resources ====== | ||
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| - | See also: | ||
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