Function sqlNow

Current date-and-time (instant), dialect-appropriate.

• mysql/mariadb: NOW()
• postgres/cockroachdb/redshift: NOW()
• mssql: GETDATE()
• oracle: SYSTIMESTAMP
• sqlite: datetime('now')
• db2: CURRENT TIMESTAMP (special register, no parentheses)
• snowflake: CURRENT_TIMESTAMP()
• clickhouse: now()