--- /dev/null
+
+1. OVERVIEW
+
+ This README file describes the syntax of the arguments that may be passed to
+ the FTS3 MATCH operator used for full-text queries. For example, if table
+ "t1" is an Fts3 virtual table, the following SQL query:
+
+ SELECT * FROM t1 WHERE <col> MATCH <full-text query>
+
+ may be used to retrieve all rows that match a specified for full-text query.
+ The text "<col>" should be replaced by either the name of the fts3 table
+ (in this case "t1"), or by the name of one of the columns of the fts3
+ table. <full-text-query> should be replaced by an SQL expression that
+ computes to a string containing an Fts3 query.
+
+ If the left-hand-side of the MATCH operator is set to the name of the
+ fts3 table, then by default the query may be matched against any column
+ of the table. If it is set to a column name, then by default the query
+ may only match the specified column. In both cases this may be overriden
+ as part of the query text (see sections 2 and 3 below).
+
+ As of SQLite version 3.6.8, Fts3 supports two slightly different query
+ formats; the standard syntax, which is used by default, and the enhanced
+ query syntax which can be selected by compiling with the pre-processor
+ symbol SQLITE_FTS3_ENABLE_PARENTHESIS defined.
+
+ -DSQLITE_FTS3_ENABLE_PARENTHESIS
+
+2. STANDARD QUERY SYNTAX
+
+ When using the standard Fts3 query syntax, a query usually consists of a
+ list of terms (words) separated by white-space characters. To match a
+ query, a row (or column) of an Fts3 table must contain each of the specified
+ terms. For example, the following query:
+
+ <col> MATCH 'hello world'
+
+ matches rows (or columns, if <col> is the name of a column name) that
+ contain at least one instance of the token "hello", and at least one
+ instance of the token "world". Tokens may be grouped into phrases using
+ quotation marks. In this case, a matching row or column must contain each
+ of the tokens in the phrase in the order specified, with no intervening
+ tokens. For example, the query:
+
+ <col> MATCH '"hello world" joe"
+
+ matches the first of the following two documents, but not the second or
+ third:
+
+ "'Hello world', said Joe."
+ "One should always greet the world with a cheery hello, thought Joe."
+ "How many hello world programs could their be?"
+
+ As well as grouping tokens together by phrase, the binary NEAR operator
+ may be used to search for rows that contain two or more specified tokens
+ or phrases within a specified proximity of each other. The NEAR operator
+ must always be specified in upper case. The word "near" in lower or mixed
+ case is treated as an ordinary token. For example, the following query:
+
+ <col> MATCH 'engineering NEAR consultancy'
+
+ matches rows that contain both the "engineering" and "consultancy" tokens
+ in the same column with not more than 10 other words between them. It does
+ not matter which of the two terms occurs first in the document, only that
+ they be seperated by only 10 tokens or less. The user may also specify
+ a different required proximity by adding "/N" immediately after the NEAR
+ operator, where N is an integer. For example:
+
+ <col> MATCH 'engineering NEAR/5 consultancy'
+
+ searches for a row containing an instance of each specified token seperated
+ by not more than 5 other tokens. More than one NEAR operator can be used
+ in as sequence. For example this query:
+
+ <col> MATCH 'reliable NEAR/2 engineering NEAR/5 consultancy'
+
+ searches for a row that contains an instance of the token "reliable"
+ seperated by not more than two tokens from an instance of "engineering",
+ which is in turn separated by not more than 5 other tokens from an
+ instance of the term "consultancy". Phrases enclosed in quotes may
+ also be used as arguments to the NEAR operator.
+
+ Similar to the NEAR operator, one or more tokens or phrases may be
+ separated by OR operators. In this case, only one of the specified tokens
+ or phrases must appear in the document. For example, the query:
+
+ <col> MATCH 'hello OR world'
+
+ matches rows that contain either the term "hello", or the term "world",
+ or both. Note that unlike in many programming languages, the OR operator
+ has a higher precedence than the AND operators implied between white-space
+ separated tokens. The following query matches documents that contain the
+ term 'sqlite' and at least one of the terms 'fantastic' or 'impressive',
+ not those that contain both 'sqlite' and 'fantastic' or 'impressive':
+
+ <col> MATCH 'sqlite fantastic OR impressive'
+
+ Any token that is part of an Fts3 query expression, whether or not it is
+ part of a phrase enclosed in quotes, may have a '*' character appended to
+ it. In this case, the token matches all terms that begin with the characters
+ of the token, not just those that exactly match it. For example, the
+ following query:
+
+ <col> MATCH 'sql*'
+
+ matches all rows that contain the term "SQLite", as well as those that
+ contain "SQL".
+
+ A token that is not part of a quoted phrase may be preceded by a '-'
+ character, which indicates that matching rows must not contain the
+ specified term. For example, the following:
+
+ <col> MATCH '"database engine" -sqlite'
+
+ matches rows that contain the phrase "database engine" but do not contain
+ the term "sqlite". If the '-' character occurs inside a quoted phrase,
+ it is ignored. It is possible to use both the '-' prefix and the '*' postfix
+ on a single term. At this time, all Fts3 queries must contain at least
+ one term or phrase that is not preceded by the '-' prefix.
+
+ Regardless of whether or not a table name or column name is used on the
+ left hand side of the MATCH operator, a specific column of the fts3 table
+ may be associated with each token in a query by preceding a token with
+ a column name followed by a ':' character. For example, regardless of what
+ is specified for <col>, the following query requires that column "col1"
+ of the table contains the term "hello", and that column "col2" of the
+ table contains the term "world". If the table does not contain columns
+ named "col1" and "col2", then an error is returned and the query is
+ not run.
+
+ <col> MATCH 'col1:hello col2:world'
+
+ It is not possible to associate a specific table column with a quoted
+ phrase or a term preceded by a '-' operator. A '*' character may be
+ appended to a term associated with a specific column for prefix matching.
+
+3. ENHANCED QUERY SYNTAX
+
+ The enhanced query syntax is quite similar to the standard query syntax,
+ with the following four differences:
+
+ 1) Parenthesis are supported. When using the enhanced query syntax,
+ parenthesis may be used to overcome the built-in precedence of the
+ supplied binary operators. For example, the following query:
+
+ <col> MATCH '(hello world) OR (simple example)'
+
+ matches documents that contain both "hello" and "world", and documents
+ that contain both "simple" and "example". It is not possible to forumlate
+ such a query using the standard syntax.
+
+ 2) Instead of separating tokens and phrases by whitespace, an AND operator
+ may be explicitly specified. This does not change query processing at
+ all, but may be used to improve readability. For example, the following
+ query is handled identically to the one above:
+
+ <col> MATCH '(hello AND world) OR (simple AND example)'
+
+ As with the OR and NEAR operators, the AND operator must be specified
+ in upper case. The word "and" specified in lower or mixed case is
+ handled as a regular token.
+
+ 3) The '-' token prefix is not supported. Instead, a new binary operator,
+ NOT, is included. The NOT operator requires that the query specified
+ as its left-hand operator matches, but that the query specified as the
+ right-hand operator does not. For example, to query for all rows that
+ contain the term "example" but not the term "simple", the following
+ query could be used:
+
+ <col> MATCH 'example NOT simple'
+
+ As for all other operators, the NOT operator must be specified in
+ upper case. Otherwise it will be treated as a regular token.
+
+ 4) Unlike in the standard syntax, where the OR operator has a higher
+ precedence than the implicit AND operator, when using the enhanced
+ syntax implicit and explict AND operators have a higher precedence
+ than OR operators. Using the enhanced syntax, the following two
+ queries are equivalent:
+
+ <col> MATCH 'sqlite fantastic OR impressive'
+ <col> MATCH '(sqlite AND fantastic) OR impressive'
+
+ however, when using the standard syntax, the query:
+
+ <col> MATCH 'sqlite fantastic OR impressive'
+
+ is equivalent to the enhanced syntax query:
+
+ <col> MATCH 'sqlite AND (fantastic OR impressive)'
+
+ The precedence of all enhanced syntax operators, in order from highest
+ to lowest, is:
+
+ NEAR (highest precedence, tightest grouping)
+ NOT
+ AND
+ OR (lowest precedence, loosest grouping)
+
+ Using the advanced syntax, it is possible to specify expressions enclosed
+ in parenthesis as operands to the NOT, AND and OR operators. However both
+ the left and right hand side operands of NEAR operators must be either
+ tokens or phrases. Attempting the following query will return an error:
+
+ <col> MATCH 'sqlite NEAR (fantastic OR impressive)'
+
+ Queries of this form must be re-written as:
+
+ <col> MATCH 'sqlite NEAR fantastic OR sqlite NEAR impressive'
+
+
+
projects / thirdparty / sqlite.git / commitdiff
