Exasol dialect: Add support for JSON_VALUE

[nnamdi16]

Description

SQLGlot currently does not support the JSON_VALUE function in the Exasol dialect.

When parsing Exasol SQL containing JSON_VALUE, SQLGlot either:

• fails to parse, or
• does not generate correct Exasol SQL

Parent issue: tobymao#6695

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Example

SELECT JSON_VALUE(data, '$.user.name')
FROM users;

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Current Behaviour

SQLGlot does not correctly parse and generate this function in the Exasol dialect.

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Expected Behaviour

SQLGlot should fully support parsing and generating JSON_VALUE for the Exasol dialect.

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Proposed solution

Add:
• Parser support
• Expression support
• Generator support

for JSON_VALUE in the Exasol dialect.

[nnamdi16]

The issue has been resolved : tobymao#7088