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Length limit requirements of DM7 for various database table names and field names

2025-01-17 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Database >

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This article introduces the relevant knowledge of "DM7 for all kinds of database table names and field names length limit requirements", in the actual case operation process, many people will encounter such a dilemma, then let the editor lead you to learn how to deal with these situations! I hope you can read it carefully and be able to achieve something!

One problem

In the process of business upgrade, the change of database structure is involved, and the fields of some tables are renamed. In the process of modifying the field names of the table, the problem of "illegal marker length" is encountered, as shown in the following figure:

Let's make it clear here that for DM7 databases, the number of named bytes of objects such as table names and field names is limited to 128bytes and cannot be changed! For more information, see the instructions in the 3.6.1 base table definition statement in the DM7_SQL language user Manual. The excerpt is as follows:

Requirements for table names:

Indicates the base table name to be created, with a maximum length of 128 bytes; in the case of a partitioned table, the main table name and partition name follow the "master table name + partition name" total length of no more than 128 bytes.

Requirements for listing:

Indicates the column name in the base table, with a maximum length of 128 bytes

In fact, we can conclude by looking at the dynamic performance view of the DM7 database:

SQL > desc USER_TAB_COLS Line number name type$ nullable--1 TABLE_NAME VARCHAR (128) N2 COLUMN_NAME VARCHAR (128) N3 DATA_TYPE VARCHAR (128) N4 DATA _ TYPE_MOD VARCHAR (3) Y5 DATA_TYPE_OWNER VARCHAR Y6 DATA_LENGTH NUMBER Y7 DATA_PRECISION NUMBER Y8 DATA_SCALE NUMBER Y9 NULLABLE VARCHAR (1) Y10 COLUMN_ID NUMBER Y11 DEFAULT_LENGTH NUMBER Y Line number name Type$ nullable--12 DATA_DEFAULT TEXT Y13 NUM_DISTINCT NUMBER Y14 LOW_VALUE VARBINARY (32) Y15 HIGH_VALUE VARBINARY (32) Y16 DENSITY NUMBER Y … Too much output is omitted here

In the above output, we can clearly see that DM7 limits the length of table and column names; of course, in the actual production environment, it is difficult to encounter a table whose column name exceeds 128bytes, unless. (please make up your brains.)

Second summary

To sum up, the length restrictions for various database table names and field names are as follows:

Database table name length limit field name length limit oracle3030mysql6464db2128128access6464sqlserver128128dm7128128dm8128128 "DM7 length limit requirements for all kinds of database table names and field names" is introduced here, thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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