With the aim of providing the complete demography of galaxies in the local Universe, including their nuclear properties, we present SPRING, a complete census of local galaxies limited to the spring quarter of the Northern sky (10h<RA<16h; 0{deg}<Dec<65{deg}). The SPRING catalogue is a flux- and volume-limited sample (r<17.7mag, cz<10000km/s) of 30597 galaxies, including the Virgo, Coma and A1367 clusters. Images and spectra were individually examined to clear the sample from unwanted entries. To inspect possible secular and environmental dependencies of the various nuclear excitation properties (SF vs. AGN), we perform a multidimensional analysis by dividing the total sample according to (i) their position in the (NUV-i) vs. Mstar diagram, (ii) local galaxy density, (iii) stellar-mass, (iv) halo-mass of the group to which galaxies belong, and (v) neutral Hydrogen content. We present a new calibration of the optical diameter-based HI-deficiency parameter HIdef employing a reference sample of isolated galaxies extracted from SPRING. At intermediate distances between Virgo and Coma, we identify a ring-like structure of galaxies constituted by three large filaments, each with approximately 20h^-1^Mpc length, mostly composed of blue-cloud galaxies with stellar-mass Mstar<~10^10^M_{sun}_. The fraction of HI-deficient galaxies within the filament (30%) suggests that filaments are a transitioning environment between field and cluster in terms of HI content, as we find a clear progression from field galaxies to filament and cluster galaxies for increasing HIdef parameter. We classify the nuclear spectra according to the four-line BPT and the two-line WHAN diagnostic diagrams, and investigate the variation in the fraction of active nuclei hosts with stellar-mass, as well as their colours and environments. We observe that the fraction of LINERs is a steep function of stellar-mass, e.g., it is consistent with zero up to Mstar>~10^9.5^M_{sun}_ and becomes 40% for Mstar<~10^10.5^M_{sun}_, whereas, for Mstar<~10^9-9:5^M_{sun}_, almost the entire spectroscopic sample is constituted of galaxies with starforming nuclei. We investigate whether the nuclear-excitation fractions depend predominantly on the stellar-mass or, conversely, on the galaxy environment. In general, we observe that the mass-dependency of the fraction of Seyfert nuclei is little sensitive to the galaxy environment, whereas the fraction of star-forming nuclei is a steeper function of stellar-mass in lower-density environments and in blue-cloud galaxies. We find that the fraction of LINERs depends on galaxy colour and, for Mstar>~10^9.510^M_{sun}_, increases in galaxies belonging to the green valley.