---
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  - https://ydb-platform--ydb.viewer.diplodoc.com/en/yql/reference/syntax/select/fulltext_index.md
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sourcePath: en/core/yql/reference/syntax/select/fulltext_index.md
---
> **Documentation Index:** Fetch the complete configuration index at https://ydb-platform--ydb.viewer.diplodoc.com/en/llms.txt

# VIEW (Fulltext index)

To select data from a row-oriented table using a [fulltext index](https://ydb-platform--ydb.viewer.diplodoc.com/en/dev/fulltext-indexes.md), use the `VIEW` expression:

```yql
SELECT ...
FROM TableName VIEW IndexName
WHERE FulltextMatch(TextColumn, "query")
ORDER BY ...
```

{% note info %}

A fulltext index isn't automatically selected by the [optimizer](https://ydb-platform--ydb.viewer.diplodoc.com/en/concepts/glossary.md#optimizer) and must be specified explicitly using `VIEW IndexName`.

Fulltext search functions (`FulltextMatch`, `FulltextScore`) require `VIEW`. If `VIEW` isn't used, the query fails.

Only one fulltext predicate is supported per read through `VIEW`. `FulltextMatch` / `FulltextScore` can't be used under `OR` or `NOT`.
For relevance access, you must include `FulltextScore(...) > 0` in `WHERE`.

For function details, see [Fulltext search](https://ydb-platform--ydb.viewer.diplodoc.com/en/yql/reference/builtins/fulltext.md), including
[FulltextMatch](https://ydb-platform--ydb.viewer.diplodoc.com/en/yql/reference/builtins/fulltext.md#fulltext-match) and
[FulltextScore](https://ydb-platform--ydb.viewer.diplodoc.com/en/yql/reference/builtins/fulltext.md#fulltext-score).

{% endnote %}

## FulltextMatch

[FulltextMatch(text, query)](https://ydb-platform--ydb.viewer.diplodoc.com/en/yql/reference/builtins/fulltext.md#fulltext-match) filters rows by whether the text matches the fulltext query:

```yql
SELECT id, title
FROM articles VIEW ft_idx
WHERE FulltextMatch(body, "machine learning")
LIMIT 20;
```

Only the first two arguments can be positional. Additional parameters must be passed as **named arguments**:

* `Mode` (String): query mode:
  * `Keywords` (default) — the query is split into individual terms; how they are combined is determined by `DefaultOperator`
  * `Query` — extended syntax with logical operators: required terms via `+`, excluded terms via `-`, exact phrases in double quotes
  * `Wildcard` — wildcard search: `%` matches any substring, `_` matches a single character (similar to `LIKE`); requires an n-gram index
* `DefaultOperator` (String): term combination operator in `Keywords` mode:
  * `And` (default) — all query terms must be present in the text
  * `Or` — matching at least one term is sufficient; use `MinimumShouldMatch` to set a minimum threshold
* `MinimumShouldMatch` (String): minimum number of matched terms when `DefaultOperator = "Or"` — specified as an absolute number (for example, `"3"`) or a percentage of query terms (for example, `"50%"`)

### `Wildcard` mode and `%` / `_` patterns (requires n-grams)

If the index is created with n-gram filtering, you can use `%` and `_` patterns similar to `LIKE`.
To explicitly enable this behavior, pass `"Wildcard" AS Mode` as a named argument:

```yql
SELECT id, title
FROM articles VIEW ft_idx
WHERE FulltextMatch(body, "mach% learn%", "Wildcard" AS Mode)
LIMIT 20;
```

### LIKE / ILIKE (use the fulltext index)

For fulltext indexes with n-grams, `LIKE`/`ILIKE` predicates over the indexed text column use the same logic as `FulltextMatch(..., "Wildcard" AS Mode)`:

```yql
SELECT id, title
FROM articles VIEW ft_idx
WHERE body ILIKE "%learn%ing%"
LIMIT 20;
```

## FulltextScore ([BM25](https://en.wikipedia.org/wiki/Okapi_BM25) relevance)

[FulltextScore(text, query)](https://ydb-platform--ydb.viewer.diplodoc.com/en/yql/reference/builtins/fulltext.md#fulltext-score) returns a relevance score and can be used for ranking.
Relevance scoring requires the [fulltext_relevance](https://ydb-platform--ydb.viewer.diplodoc.com/en/dev/fulltext-indexes.md#relevance) index type.

```yql
SELECT id, title, FulltextScore(body, "machine learning") AS relevance
FROM articles VIEW ft_idx
WHERE FulltextScore(body, "machine learning") > 0
ORDER BY relevance DESC
LIMIT 10;
```

### Optional parameters

Additional parameters must be passed as **named arguments**:

* `DefaultOperator` (String): term combination operator — `And` (default, all terms must be present) or `Or` (at least one term must match)
* `MinimumShouldMatch` (String): when `DefaultOperator = "Or"`, minimum number of matched terms — specified as an absolute number (for example, `"2"`) or a percentage (for example, `"50%"`)
* `K1` (Double): term frequency saturation parameter in [BM25](https://en.wikipedia.org/wiki/Okapi_BM25) — controls how strongly repeated occurrences of a term affect the score; typical range: 1.2–2.0
* `B` (Double): document length normalization parameter in [BM25](https://en.wikipedia.org/wiki/Okapi_BM25) — `0.0` disables normalization, `1.0` fully normalizes by document length; typical value: 0.75

Example:

```yql
SELECT id, FulltextScore(body, "machine learning", "Or" AS DefaultOperator, "50%" AS MinimumShouldMatch) AS relevance
FROM articles VIEW ft_idx
WHERE FulltextScore(body, "machine learning", "Or" AS DefaultOperator, "50%" AS MinimumShouldMatch) > 0
ORDER BY relevance DESC;
```

{% note info %}

Only the first two arguments of `FulltextMatch` / `FulltextScore` can be positional. Use named arguments for all additional parameters.

The `FulltextScore(...)` expression is repeated in full in both `SELECT` and `WHERE` — YQL, like standard SQL, evaluates `WHERE` before `SELECT`, so aliases defined in `SELECT` are not available in `WHERE`. Both occurrences must be identical.

{% endnote %}