Telling my shader when to use which Texture

Question

So I've just managed to get Texturing via GLSL shaders to work and i can pass a sampler2d textureHandler + my uv coordinates into my shader to specify the texture to be displayed on my Tiles.

Now im Wondering how I could define which tile should get which Texture cause right now I can only put 1 single texture on ALL tiles I have...

My vertex shader:

in vec3 position; 
in vec2 vertexUV;

uniform mat4 orthoMatrix;

out vec2 UV;

void main()
{
    gl_Position = orthoMatrix * vec4(position, 1.0);
    UV = vertexUV;
}

my fragment shader:

in vec2 UV;

out vec4 outColor;

uniform sampler2D myTextureSampler1;

void main()
{
    outColor = texture2D(myTextureSampler1, UV);
}

My Texture Loading right now looks like this: http://puu.sh/62MhS.png

Answer 1

"myTextureSampler1" should be a big texture containing all your tiles (Texture Atlas). This way, all you need to do is pass the right UV for each tile.