Use of AND, OR, comparisons in WHERE .Decided to include INNER JOINS so that information was more readable rather than just numbers.

/*Query 1 - List those signs that would be considered "Banners" based on dimensions and material*/
SELECT CONCAT(Signs.hor_dimens, ' ft x ', Signs.vert_dimens, ' ft') as 'Banners', Materials.name as 'Material', Finishes.name as 'Finish', Signs.quantity as 'Quantity', Signs.cost as 'Cost'
FROM Signs 
INNER JOIN Materials ON Signs.mat_id=Materials.mat_id
INNER JOIN Finishes ON Signs.finish_id=Finishes.finish_id
WHERE (Signs.hor_dimens>4 or Signs.vert_dimens>4) and Signs.mat_id != 5 and Signs.mat_id != 6;
/*Query 2 - List those signs that would be considered "Posters" based on dimensions and material*/
SELECT CONCAT(Signs.hor_dimens, ' ft x ', Signs.vert_dimens, ' ft') as 'Posters', Materials.name as 'Material', Finishes.name as 'Finish', Signs.quantity as 'Quantity', Signs.cost as 'Cost'
FROM Signs 
INNER JOIN Materials ON Signs.mat_id=Materials.mat_id
INNER JOIN Finishes ON Signs.finish_id=Finishes.finish_id
WHERE (Signs.hor_dimens<4 and Signs.vert_dimens<4) and Signs.mat_id != 5 and Signs.mat_id != 6;
/*Query 3 - List those signs that are printed on adhesive material*/
SELECT CONCAT(Signs.hor_dimens, ' ft x ', Signs.vert_dimens, ' ft') as 'Adhesive Signs', Materials.name as 'Material', Finishes.name as 'Finish', Signs.quantity as 'Quantity', Signs.cost as 'Cost'
FROM Signs 
INNER JOIN Materials ON Signs.mat_id=Materials.mat_id
INNER JOIN Finishes ON Signs.finish_id=Finishes.finish_id
WHERE Signs.mat_id = 5 or Signs.mat_id = 6;
/*Query 4 - List those signs that can be used outside by excluding those with certain materials*/
SELECT CONCAT(Signs.hor_dimens, ' ft x ', Signs.vert_dimens, ' ft') as 'Outdoor Ready', Materials.name as 'Material', Finishes.name as 'Finish', Signs.quantity as 'Quantity', Signs.cost as 'Cost'
FROM Signs 
INNER JOIN Materials ON Signs.mat_id=Materials.mat_id
INNER JOIN Finishes ON Signs.finish_id=Finishes.finish_id
WHERE Signs.mat_id != 4 and Signs.mat_id != 6;