Difference between revisions of "SQL queries"
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| − | SQL, often referred to as Structured Query Language | + | SQL, often referred to as Structured Query Language, is a database computer language designed for managing data in relational database management systems (RDBMS), and originally based upon relational algebra. |
A SQL query is composed normally by clausule SELECT and optionally FROM, WHERE and ORDER BY. | A SQL query is composed normally by clausule SELECT and optionally FROM, WHERE and ORDER BY. | ||
== SELECT == | == SELECT == | ||
| − | Used to | + | Used to specify a property list ( columns ) by name that will apppear in results. The character * indicates all properties are selected. |
== FROM == | == FROM == | ||
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</source> | </source> | ||
| − | There's some limitation there's no | + | There's some limitation there's no equivalent with this XPath query in SQL. There's a limitation in SQL to using CONTAINS in a descendant query. |
<source lang="xml"> | <source lang="xml"> | ||
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== ORDER BY == | == ORDER BY == | ||
| − | Used to ordering results. Normally used the jcr:score property. | + | Used to sort (control ordering of) results. Normally used the jcr:score property. |
=== Documents that contains linux ordered by score === | === Documents that contains linux ordered by score === | ||
Revision as of 12:58, 13 July 2011
SQL, often referred to as Structured Query Language, is a database computer language designed for managing data in relational database management systems (RDBMS), and originally based upon relational algebra.
A SQL query is composed normally by clausule SELECT and optionally FROM, WHERE and ORDER BY.
SELECT
Used to specify a property list ( columns ) by name that will apppear in results. The character * indicates all properties are selected.
FROM
Defines the nodes type ( tables ) selected.
Select all keyword in all documents
SELECT okm:keywords FROM okm:document
okm:keyword is an okm:document property. The nodes in repository has a hierarchical structure; the base type is nt:base: This type must be used to search all nodes (FROM nt:base)
WHERE
Used to filter selected rows by some criteria.
Select all documents with keywords not empty
SELECT okm:author, okm:keywords FROM okm:document WHERE okm:keywords <> ''
Operators evaluation order:
- ()
- operators: <, >, =, <=, >=, <>, LIKE, IS NULL, IS NOT NULL
- functions: CONTAINS
- logic opertors: NOT, AND, OR
LIKE
Used for pattern purposes in where clausule
Documents name starting with linux
SELECT * FROM okm:document WHERE okm:name LIKE 'linux%'
CONTAINS
Used to full text searching ( the indexed content )
Documents that contains jackrabbit
SELECT * FROM okm:resource WHERE CONTAINS(., 'jackrabbit')
There's some limitation there's no equivalent with this XPath query in SQL. There's a limitation in SQL to using CONTAINS in a descendant query.
//element(*, okm:document)[jcr:contains(okm:content, 'linux')]
ORDER BY
Used to sort (control ordering of) results. Normally used the jcr:score property.
Documents that contains linux ordered by score
SELECT * FROM okm:document WHERE CONTAINS(., 'linux') ORDER BY jcr:score DESC
Property jcr:path
Always it'll appear in results and indicates the full node path. jcr:path it can be used in queries like:
Exact search
jcr:path='/books/mybooks/EffectiveJava'
Searching for children
jcr:path LIKE '/books/%' AND NOT jcr:path LIKE '/books/%/%'
Descendants
jcr:path LIKE '/books/mybooks/%'
