使用SQL查询创建过滤器

Question

I am trying to create a filter with SQL queries but am having trouble with numeric values linking to other tables.

Every time I try to link to another table, it takes the same record and repeats it for every element in the other table.

For example, here is query:

SELECT
ELEMENTS.RID,TAXONOMIES.SHORT_DESCRIPTION,[type],ELEMENT_NAME,ELEMENT_ID,SUBSTITUTION_GROUPS.DESCRIPTION,namespace_prefix,datatype_localname
FROM
ELEMENTS,SUBSTITUTION_GROUPS,TAXONOMIES,SCHEMAS,DATA_TYPES
WHERE
ELEMENTS.TAXONOMY_ID = TAXONOMIES.RID AND ELEMENTS.ELEMENT_SCHEMA_ID = SCHEMAS.RID
AND ELEMENTS.DATA_TYPE_ID = DATA_TYPES.RID
AND ELEMENTS.SUBSTITUTION_GROUP_ID = 0

The last line is the actual filtering criteria.

Here is an example result:

There should only be ONE result (Item has an RID of 0). But it's repeating a copy of the one record for every result inside the substitution groups table (there's 4).

Here is my database schema for reference. The lines indicate relationships between tables and the circles indicate the values I want:

Answer 1

You're forgot to join between ELEMENTS and SUBSTITUTION_GROUPS in your query.

SELECT
ELEMENTS.RID,TAXONOMIES.SHORT_DESCRIPTION,[type],ELEMENT_NAME,ELEMENT_ID,SUBSTITUTION_GROUPS.DESCRIPTION,namespace_prefix,datatype_localname
FROM
ELEMENTS,SUBSTITUTION_GROUPS,TAXONOMIES,SCHEMAS,DATA_TYPES
WHERE
ELEMENTS.TAXONOMY_ID = TAXONOMIES.RID AND ELEMENTS.ELEMENT_SCHEMA_ID = SCHEMAS.RID
AND ELEMENTS.DATA_TYPE_ID = DATA_TYPES.RID
AND ELEMENTS.SUBSTITUTION_GROUP_ID = SUBSTITUTION_GROUPS.RID
AND ELEMENTS.SUBSTITUTION_GROUP_ID = 0