Database schema:

CREATE TABLE "Classification" (
	"GeneID" TEXT NOT NULL -- example: ['G234064', 'G234065'],
	"Localization" TEXT NOT NULL -- example: ['cytoplasm', 'cytoskeleton'],
	PRIMARY KEY ("GeneID")
)


CREATE TABLE "Genes" (
	"GeneID" TEXT NOT NULL -- example: ['G234064', 'G234065'],
	"Essential" TEXT NOT NULL -- example: ['Essential', 'Non-Essential'],
	"Class" TEXT NOT NULL -- example: ['GTP/GDP-exchange factors (GEFs)', 'ATPases'],
	"Complex" TEXT -- example: ['?', 'Translation complexes'],
	"Phenotype" TEXT NOT NULL -- example: ['?', 'Mating and sporulation defects'],
	"Motif" TEXT NOT NULL -- example: ['PS00824', 'PS00825'],
	"Chromosome" INTEGER NOT NULL -- example: ['2', '1'],
	"Function" TEXT NOT NULL -- example: ['PROTEIN SYNTHESIS', 'CELLULAR ORGANIZATION (proteins are localized to t'],
	"Localization" TEXT NOT NULL -- example: ['cytoplasm', 'cytoskeleton'],
	CONSTRAINT fk_genes_classification FOREIGN KEY("GeneID") REFERENCES "Classification" ("GeneID")
)


CREATE TABLE "Interactions" (
	"GeneID1" TEXT NOT NULL -- example: ['G234064', 'G234065'],
	"GeneID2" TEXT NOT NULL -- example: ['G234126', 'G235065'],
	"Type" TEXT NOT NULL -- example: ['Genetic', 'Genetic-Physical'],
	"Expression_Corr" REAL NOT NULL -- example: ['0.751584888', '0.914095071'],
	PRIMARY KEY ("GeneID1", "GeneID2"), 
	CONSTRAINT fk_interactions_classification FOREIGN KEY("GeneID1") REFERENCES "Classification" ("GeneID"),
	CONSTRAINT fk_interactions_classification FOREIGN KEY("GeneID2") REFERENCES "Classification" ("GeneID")
)

Question: How many non-essential genes are located in the nucleus?

SQL:
SELECT COUNT(T1.GeneID) FROM Genes AS T1 INNER JOIN Classification AS T2 ON T1.GeneID = T2.GeneID WHERE T2.Localization = 'nucleus' AND T1.Essential = 'Non-Essential'