The NGL database is organized into tables that are related to each other via keys. To query the database, you will need to understand the organizational structure of the database, called the schema. The database schema is documented at the following URL:
https://nextgenerationliquefaction.org/schema/index.html
Figure 1 describes the schema for the SITE table, which is a high level table in the NGL database where users enter information about a particular site they have investigated following an earthquake. The SITE table contains SITE_ID, which is the primary key for the SITE table. Every entry in the SITE table is assigned a unique SITE_ID that identifies the entry. Additional fields include SITE_NAME, SITE_LAT, SITE_LON, SITE_GEOL, SITE_REM, SITE_STAT, and SITE_REVW. The Children column in Figure 1 identifies other tables in the NGL database that have been assigned a foreign key constraint to the SITE_ID field. For example, FLDO is a table containing field observations of liquefaction at a site. The FLDO table has a SITE_ID field, called a foreign key, that identifies the observation as being associated with the site with the same SITE_ID.
