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171 lines
3.9 KiB
Text
171 lines
3.9 KiB
Text
[[esql-syntax]]
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=== {esql} syntax reference
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++++
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<titleabbrev>Syntax reference</titleabbrev>
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++++
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[discrete]
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[[esql-basic-syntax]]
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=== Basic syntax
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An {esql} query is composed of a <<esql-commands,source command>> followed
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by an optional series of <<esql-commands,processing commands>>,
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separated by a pipe character: `|`. For example:
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[source,esql]
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----
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source-command
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| processing-command1
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| processing-command2
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----
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The result of a query is the table produced by the final processing command.
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For an overview of all supported commands, functions, and operators, refer to <<esql-commands>> and <<esql-functions-operators>>.
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[NOTE]
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====
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For readability, this documentation puts each processing command on a new
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line. However, you can write an {esql} query as a single line. The following
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query is identical to the previous one:
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[source,esql]
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----
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source-command | processing-command1 | processing-command2
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----
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====
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[discrete]
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[[esql-identifiers]]
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==== Identifiers
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Identifiers need to be quoted with backticks (+{backtick}+) if:
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* they don't start with a letter, `_` or `@`
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* any of the other characters is not a letter, number, or `_`
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For example:
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[source,esql]
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----
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FROM index
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| KEEP `1.field`
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----
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When referencing a function alias that itself uses a quoted identifier, the
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backticks of the quoted identifier need to be escaped with another backtick. For
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example:
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[source,esql]
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----
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FROM index
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| STATS COUNT(`1.field`)
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| EVAL my_count = `COUNT(``1.field``)`
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----
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[discrete]
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[[esql-literals]]
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==== Literals
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{esql} currently supports numeric and string literals.
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[discrete]
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[[esql-string-literals]]
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===== String literals
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A string literal is a sequence of unicode characters delimited by double
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quotes (`"`).
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[source,esql]
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----
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// Filter by a string value
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FROM index
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| WHERE first_name == "Georgi"
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----
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If the literal string itself contains quotes, these need to be escaped (`\\"`).
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{esql} also supports the triple-quotes (`"""`) delimiter, for convenience:
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[source,esql]
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----
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ROW name = """Indiana "Indy" Jones"""
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----
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The special characters CR, LF and TAB can be provided with the usual escaping:
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`\r`, `\n`, `\t`, respectively.
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[discrete]
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[[esql-numeric-literals]]
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===== Numerical literals
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The numeric literals are accepted in decimal and in the scientific notation
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with the exponent marker (`e` or `E`), starting either with a digit, decimal
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point `.` or the negative sign `-`:
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[source, sql]
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----
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1969 -- integer notation
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3.14 -- decimal notation
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.1234 -- decimal notation starting with decimal point
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4E5 -- scientific notation (with exponent marker)
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1.2e-3 -- scientific notation with decimal point
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-.1e2 -- scientific notation starting with the negative sign
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----
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The integer numeric literals are implicitly converted to the `integer`, `long`
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or the `double` type, whichever can first accommodate the literal's value.
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The floating point literals are implicitly converted the `double` type.
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To obtain constant values of different types, use one of the numeric
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<<esql-type-conversion-functions, conversion functions>>.
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[discrete]
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[[esql-comments]]
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==== Comments
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{esql} uses C++ style comments:
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* double slash `//` for single line comments
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* `/*` and `*/` for block comments
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[source,esql]
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----
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// Query the employees index
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FROM employees
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| WHERE height > 2
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----
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[source,esql]
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----
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FROM /* Query the employees index */ employees
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| WHERE height > 2
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----
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[source,esql]
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----
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FROM employees
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/* Query the
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* employees
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* index */
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| WHERE height > 2
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----
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[discrete]
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[[esql-timespan-literals]]
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==== Timespan literals
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Datetime intervals and timespans can be expressed using timespan literals.
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Timespan literals are a combination of a number and a temporal unit. The
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supported temporal units are listed in <<esql-time-spans-table, time span unit>>.
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More examples of the usages of time spans can be found in
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<<esql-time-spans, Use time spans in ES|QL>>.
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Timespan literals are not whitespace sensitive. These expressions are all valid:
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* `1day`
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* `1 day`
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* `1 day`
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